Do you get confused when you run native apps on your Mac? Like, you can't recall which app does which because they all use native controls with a standard L & F? If you do, this is a usability concern I've not heard of and would love more research into. Most usability studies focus on how effectively one can perform a task in an app, not how quickly one can recollect which application performs which function for them, so it may just not be well-studied.