Why?
Where I'm from, the word "collaborator" is universally associated with collaborating with either the communist regime or the nazi occupant. Does it make the word bad? Should github change it to something else? Look beyond your own culture and you'll soon find that no word is safe to use.
Also, isn't Github still helping ICE build concentration camps for kids? And yet the hypothetically offensive meaning of "master" is where they draw the line?
And yes, they are a pain in the ass when it comes to changes and that's why one should be careful with unnecessary changes.