The term “GitHub flow” existed prior to the Microsoft acquisition. The GitHub documentation history would be definitive, but you can find articles dating back to 2014 discussing GitHub Flow vs GitFlow. The acquisition was in 2018.
I agree that the name isn’t the best. It is however at least specific. “Trunk based development” encompasses a class of development processes. Although I don’t think I’ve ever actually described a real world process as “GitHub Flow” because almost no one knows what it specifically is anyway.
Disclosure: I work for Microsoft.
