There's a fundamental flaw in that logic from the tweet.

YC can earn a lot more by funding competition and has a lot to lose from the community from mistreating competition or favoriting others.

I also haven't seen any evidence suggesting any.

At a scale of funding hundreds of companies/year, nothing will go perfect all the time either, i suppose.

Fyi: long time HN reader, Belgium, not affiliated and received a ( correct ) ban from dang one time ;)