I find the current text ambiguous: does it mean that these tags cannot be used in other categories, or that these are the only tags that can be used in the category? It’s the latter, and I think the text could better convey this.
I know this can be edited on a per-site basis, but I think this is probably a change worth making across the board.
I’ve therefore made a PR for it:
I like it, except I’d make the last one say “within these groups” to make sure it’s not confused with our user groups.
Just a short off topic comment, your mouse handwriting is spectacularly awesome!