Yes...but he's not making the claim that "100% of foster kids who get (some small number of adults caring about them) will be successful", he's saying that "the minimum I've observed for foster kids to be successful is (some small number of adults caring about them)".
The latter claim is perfectly valid to make when 100% of survivors have trait X; you are correct in implying that it would be invalid to say having trait X will guarantee a survivor.
> it takes a surprisingly small number of emotionally stable adults to help kids get through chaotic circumstances
The "surprising" modifier here makes the object something that needs extra context, what's surprising here is that the number is small and not large. If bio mom and bio dad and foster mom and foster dad and all the extended family and most of their teachers are distant, but their track coach is emotionally invested (thanks, Buzz), that's, surprisingly, sometimes all that it takes.
Yes, if no one's invested, that's not enough, as you'd expect. It does leave the possibility that everyone is invested and it's still not enough.
Consider the idiom it takes two to tango. Now, one of the two could be a quadriplegic, or a dog, or maybe they both come from a severe religious cult which has forbidden dancing and just can't bring themselves to do it.
That's fine; the meaning is that two are necessary, not that two are sufficient.
Saying "It takes surprisingly little time to do!" isn't trying to give a lower bound on how much time it takes. Obviously not completely unambiguous, but the "sufficient" reading is completely natural English.
It's not setting a bound at all. It -is- saying that the amount of time is "surprisingly little".
But to the topic at hand, the logical implication is that "to do it" => "takes surprisingly little time" (that is, doing it implies you took surprisingly little time)
Not "taking surprisingly little time" => "to do it" (that is, taking surprisingly little time implies you do it; after all, you might have taken surprisingly little time to do -something else-).
Same as the above; the implication is that "success" implies "(at least) a surprisingly small number of adults were involved", not that "(at least) a surprisingly small number of adults were involved" implies "success".
I find it helpful to use formal logic to explain stuff like this. If I make a statement that p => q (that is, p implies q), and that statement is true, it does NOT necessarily follow that q => p (that is, q implies p) is true (it may or may not be; it is independent from a formal logic perspective). It is necessary to evaluate q => p separately, in which case we may find it to be true, OR we may find q =/> p to be true (that is, q does not imply p; or put another way, the fact q is true tells us nothing about whether p is).
As an example, "My shoes are wet because it is raining", p = it is raining, and q = my shoes are wet. p => q means if it is raining (p), my shoes are wet (q). But it does not also follow from that that q => p; that is, just because my shoes are wet (q) it does not mean it must be raining (p; I might have, after all, been out watering the lawn). Thus, q =/> p.
For the tango example, p = a tango is possible, q = there are two people. p => q, but q =/> q (that is, two people does not imply a tango is possible).
In this case, p = foster child is successful, and q = a number of adults (sometimes a surprisingly small number) were involved with them. p => q, but q =/> p.
You're way overthinking this. If I say "it's takes surprisingly little" it's because I'm emphasizing that it does not take a lot and instead a small amount is sufficient.
Saying "it takes a surprisingly small number of emotionally stable adults to help kids " is emphasizing that it does not require a large number of stable adults and therefore a small number is sufficient. How many does it take? Surprisingly few. A few suffice. How else can you read this? You're surprised that a necessary number is small? But it's always necessary to have at least 0 stable adults and that's as small as possible - you can't get surprised that it's small! Instead you must be surprised that the sufficient number is small.
I'm not making any comment on the number of adults; I'm just responding to the original argument that "well, I know foster kids who haven't been successful, who had supportive adults", and the ensuing argument, to further explain why that isn't a negation.
The meaning of this expression has been extended to include any situation in which the two partners are by definition understood to be essential (...).
since you keep saying that you are not a native speaker, consider believing the interpretations native speakers share. stuff simply means what it means. you can believe it or not.
more generally, when someone says something you find incredulous, consider processing that internally, and then decide if saying "huh, now i know" is not a better reaction to "no way, maybe you're wrong."
I'm completely on the-dude's side on the reading of the original quote (not the tango quote) and I'm a native speaker. Moreover I find your (and the GP post) tone extremely condescending. There's no way to read the-dude's writing as "arguing". He states his readings of quotes simply without argument and clearly marking them as his personal reading (saying "to me" and "sounds"). By posting it here he's obviously inviting someone to explain why he's wrong - but the responses here are instead choosing to declare their authority on the matter and to belittle him.
And to the original point - he's not wrong. Of course from life experience we all know that there are exceptions to every rule, but the rule as written was that just a few stable adults suffices. Saying "it takes surprisingly few to tango" is completely different meaning from "it takes two to tango", so the comparison to that is not relevant (and the-dude does mistake that phrase, which is specifically used to call out that one is not enough). How many does it take? It takes surprisingly few. You have enough even if you only have a few.
The latter claim is perfectly valid to make when 100% of survivors have trait X; you are correct in implying that it would be invalid to say having trait X will guarantee a survivor.