It's more that it really doesn't matter. Noise from individual variation swamps group variation in almost every practical case, and other outward cues of ability (i.e., hard-to-fake signals) are more informative.

The main reasons to make a big deal out of group variation are, in order of how common they are:

1. You're a member of some group that dislikes the SWPL bloc and need more "soldiers" for your side of the argument
2. You have "prejudice against group X" on your bottom line and are filling in the blanks above
3. You're the kind of person who operates under some sort of weird categorical imperative to announce the truth of all propositions, regardless of instrumental value

We have a lot of epistemic rationalists here in the third category, but in most cases if you talk about the reality of group variation people will assume you are one of the first two types, which probably isn't helpful for anyone.