You have given yourself the answer....
That said, there are first party Xbox games that work better on XSX and in those cases the excuses went the other way ("MS spends more time optimizing its console version or even boycotts the PS5 version").
From there, the question becomes a little dishonest with reality. Because you have a lot of games that work better on XSX being the console with the least attention and generally PS5 being the base platform.
I don't know, maybe you're implying that in all these cases (first and3rd parties) Studios have been boycotting the PS5 version??