I am also experiencing the same issue, I wrote about it a few weeks ago:
https://discuss.grapheneos.org/d/17908-my-installed-google-play-services-version-looks-outdated/
The difference is that I actually factory defaulted my phone after the A15 update, so it is a clean install without Google Play Framework. So that is definitely not the cause.
I am not updating Google Play nor Google Play Services through GOS app store at this point in time, instead I have been waiting for them to update themselves through Google Play. But I think enough time have passed now to say for certain it is broken. Or perhaps Google Play isn't supposed to be auto-updating itself anymore since A15?