Yes, that's how GitHub calls it, but by calling everything a fork the term loses its meaning. By this definition every Chromium browser is a fork, which is just ridiculous. Edge's developers don't think of Edge as a fork
2 karma · joined September 23, 2022
https://en.wikipedia.org/wiki/Fork_(software_development)
>Eric S. Raymond, in his essay Homesteading the Noosphere,[12] stated that "The most important characteristic of a fork is that it spawns competing projects that cannot later exchange code, splitting the potential developer community"
At this point I just want to add that I'm not a developer and I don't actually know much, I just read stuff online. But yeah, Edge isn't a fork