Well, my line of thinking was that having a .ssh line in .gitignore does no harm, so I didn't consider it bloat. You could just leave it in there and it would make no difference, so it could just be completely ignored in most projects. At the same time, you would get a .gitignore file created for you, removing one of the steps you have to do now.

However, I agree with your point that allowing new devs to keep making this mistake and just shielding them from it is a bad idea. With that in mind, it might be nicer if GitHub checked for .ssh files on commit and showed a warning within the web app, letting you know what you did wrong.