This is pretty comparable to their Office suite for OSX (which admittedly is 4 years old, but the supposed 2015 Office for Mac will probably continue with a similar UI). You find this to be true with a lot of cross-platform vendors and products: Adobe, for example.

I don't have it installed on this machine currently, but doesn't Libre Office has a similar set of UI conventions as on other platforms, or is it "OSX-y"?