I've purchased some mixing courses in the past and have noticed that often there are separate left and right tracks that I'm assuming is sent to the mastering engineer. Is that a normal practice to send separate left and right tracks for mastering? In the past I've only send a single stereo wav file for mastering and that seemed fine.
I would say the "normal" is to send a stereo file, but dual mono would probably be fine. The dual mono files in the multitracks here are probably a result of protools workflow when exporting tracks and also to keep all the files mono, which for some DAWs makes it easier to import.