I sort of wondered about that thinking maybe there's only one logical way to design a git GUI on osx, but then even within this thread people brought up a few other examples that look totally different:
I switched from SourceTree to GitKraken, I don't know all the internal issues of what transpired at Atlasian on the SourceTree team, but to me it's just not the same product that the old Mac app was when they where independent.
I really like GitKraken and the team is taking feedback applying it constructively and putting out an impressive product. The part I really like is it's the same app on OSX, Linux and Windows using Electron to build it was a smart move on their part. My favorite feature has to be dropping a branch on another branch to create a pull request. I don't fanboy stuff much these days but I am a pretty big fan of their's right now.