Saying React can do it is a fact. So React devs are not spreading any FUD whatsoever.
Saying React can't do it, to paraphrase you, because "technically it's harder than with Vue" is like saying nobody can drive a stick shift because you have to shift gears manually.
Yes, you have to do it manually, no it doesn't make the car undrivable.
I gave some examples downthread where react pretty much falls apart. I'm sure you "technically" could make it work by dropping down to vanilla and cloning nodes or refactoring backend code or whatever, but at that point it's not merely "technically a bit harder", it's a pretty huge stretch.
The car gear analogy is again downplaying magnitude. The examples I gave are not a comparison between auto vs manual, it's more like auto vs getting a different license type to drive a 18 wheeler and having to learn how to turn, back out, park, go under bridges and where you're allowed to drive and not all over again. Yes, it's technically doable, no it's anywhere near similar amounts of effort as just learning stick.
To clarify, again, just because it feels like react vs vue is akin to manual vs auto when you're in a codebase that is amenable to being refactored into react, it doesn't change the fact that there are types of codebases (non-SPAs without HTTP API layers) where migrating to react is a significantly larger investment than vue. That was what the OP was saying.
I very much doubt the original comment mentioning "the most popular 3 frameworks" didn't have React in mind as one of those, even if they didn't spell it out, so that complaint IMHO makes little sense.
Saying React can't do it, to paraphrase you, because "technically it's harder than with Vue" is like saying nobody can drive a stick shift because you have to shift gears manually.
Yes, you have to do it manually, no it doesn't make the car undrivable.
That's what I call FUD.