Fun litmus test, if the person challenging this assertion happens to be a straight male: "how many guys have you slept with?"

I'd guess this depends on region/demographic, but at least in my circles on the west coast, "guys" is gendered when it's used to describe or identify people in the third person, but it's gender-neutral when used to address a group of people in the second person.

So "the guys" or "how many guys" always refers to men, but "you guys" carries no implication of gender at all. I often hear people address groups consisting entirely of women as "guys", and nobody bats an eye.

Yes agreed. In most regions/groups in America, "you guys" does not carry the same meaning as "a group of guys"

Also for reference, these are "compound nouns" - a single noun composed of multiple words. No one has these issues with "ice cream", for example, but "you guys" really is just another one of these.

I think it makes sense to say "you guys" is a compound noun, but the word "guys" can be used in this gender-neutral addressing-a-group sense outside of the phrase "you guys". For example: "Hey guys!", or "Guys, what should I eat for lunch?"

but the question was about "you guys" which is a distinct phrase that happens to share a word.

IIRC guy part is actually descended from Guy Faux, which in itself is cool.

(edit: fix grammar)

Which itself seems to be related to the word "guy" as in "guy wire" also related to "guide", "guidance", or "guidelines". Meaning to lead, direct, or conduct. To show the way.