So, in that page, after you enter the repo name, three options appear.
1. Start the repository by creating new file: it opens a github text editor. I never used this option (what kind of savage uses github's text editor???), but to be fair it creates a default branch named "main"
2. Create a new repository from the command line: run git init, etc. You get to choose the branch name, then push it to github.
3. Push your existing local repository to github. It will get whateber branch name it already had, probably "master".
So the only people affected by the change are those who use github's text editor and chose the first option. I guess not many people do that? For the most common options you get to chose the name of the branch, that by default is "master" (not that there's anything wrong with that).
Also we can argue until the cows come home about how little effort is actually involved. It could literally be a single click and it's still all still by-the-by. This is an empty virtue signal doing nothing - repeat nothing - to help the inclusion of minorities.
Sure, the name change was a stupid move in the first place. But as stupid moves go, this one fortunately does not affect my life at all (and that of most github users I guess).