It’s not just true, there’s a history of this mentioned in the replies to the original masto comment. Pixelfed is a direct competitor/alternative to instagram and meta’s has a pretty clear policy of not giving it any airtime on their platforms.
Why, well they dominate the instagram style platform space (and I’d guess it’s their biggest platform ATM and most prospective going forward). Twitter-style platforms are new for them and introduce monopoly issues … so they toy with the fediverse to allay potential issues.
I think all of the schmoozing the likes of Evan, Gargron etc are doing with meta (they have active accounts on Threads AFAIU, for instance) will reveal their true colours (techbro growth mindset just the hipster way) and leave them with egg on their face.