As I stated in Straw poll: Which governance proposals do you like best? - #20 by brettcannon, I think PEPs which give core developers the vote are within their rights to also clearly define what it means to become a core developer as it means the position now comes with new powers and responsibility.
For example, let’s say we had a “Core Dev of the Month” for whomever merged the largest number of PRs in a month. When the recognition was established all you got was your name on some website. IOW it didn’t really matter that you could game the system since the relation of receiving the “power” of being recognized didn’t really outstrip what it took to receive it.
Now imagine that one of the governance PEPs said the Core Dev of the Month got to decide on all PEPs presented the following month. Suddenly you very much care about how the Core Dev of the Month is chosen. I would argue the same is happening here: when core devs suddenly gain the vote for PEPs, you then start to care differently about how someone becomes a core dev which gives them that vote.
It will also make becoming a core dev that much more enticing to those who would like to have that sort of power with Python. While PEP 8010 and 8011 have fairly powerful positions, the voting of people into those positions helps prevent any random person walking in and saying “I think I should become the GUIDO!” But when all core devs suddenly get to vote on PEPs, that lowers the difficulty of wielding some power that we all didn’t have before.
So I do think it is totally within the scope of the governance PEPs to define what it means to become a core developer when the powers that the title bestows upon them will be increasing in a consequential manner.