So, as far as I can tell, the Nolo Press article doesn't apply to this situation, because I am traveling to DIFFERENT airports, not the SAME airport.

So it should be perfectly fine and according to the rules, which most airlines don't enforce anyway. If so, why is everyone suggesting that I HIDE the transaction by buying tickets at differnt times, or manually turning in a mileage request after the fact?

Either it is legitimate, or it is not. If it isn't, I don't want to do it. If it is, then why hide it?