You missed the point, I'm not making a spurious "whataboutism" claim.

Attribution is required by copyright.

If I take a snippet of code from stackoverflow and put it in my open source project, that's fine.

Nobody is saying it isn't.

What isn't fine is slapping a license on a file which includes that code without specifying that that code isn't subject to the license—that's claiming ownership of something which isn't yours and trying to attach a license to it.

Beyond that, you really need to re-read the stackoverflow ToS, because they don't quite say what you seem to think.