This explains my WTF moment when teaching a class full of students to push to the github classroom using push -u origin master and it being rejected and having to use main!
But as a teacher, the way this makes all the existing guides and tutorials wrong means I have to waste 15 minutes of my semester (about 1%) explaining this.
In short, the main effect of this change is to very slightly raise the barrier to entry for new developers.
Is it an empty gesture? Maybe? Does it cost more than a couple of seconds for making things clearer and making a minority of people people happy? No.
It probably wasted more integrated time across all the people reading this article than just shrugging and changing it does.