But using a different AA method, that provides a different output, is not optimization. Software optimization is about using different methods to achieve the same output.
Got your point but that's really a matter semantics then...
The output image is only the result of many, many approximations that generally try to simulate the real life. If you push your logic to the end, anything that isn't real isn't adequate. Or any cel shaded game shouldn't be allowed to exist because they fail at being truly hand drawn...
There is no "same output", only an image defined by a series of parameters, sometimes forced, sometime tweakable. There is no holy grail of IQ, just choices and tradeoffs. AA is one, so is resolution, framerate, texture used, models polycount... You don't start with a perfect picture that you then modify in good or bad ways. You build something from scratch and try to do the best you can in the fastest way possible.
To me, anything that make the process quicker is an optimization. Worthy or not, that's personal judgment, subjectivity.
Lowering image quality in order to achieve a better framerate is not optimization
This is silly. AA is only a small part of your final image. Any form of AA blurs the output, where do you set the bar of "image degradation"? Wanted to detail, but in fact, just refer to what I answered to Durante.
Absolutely not. "console optimization", in the true sense of the word, means that you were able to achieve the same image quality with less CPU and GPU resources due to coding for a specific configuration, therefore optimizing your code and getting more out of existing hardware.
Lowering image quality in order to achieve a better framerate is not optimization, it's the same thing PC gamers have been doing for decades by adjusting graphics settings! If I play Deus Ex: Human Revolution and I use FXAA instead of the more taxing (and better-lookin) MSAA, does that mean that the increased framerate is due to "PC optimizations"? Noone can possibly think that.
By your logic, anything related to image rendering can't possibly an optimization.
There is no such thing as "console optimization" and "PC optimization". Every game is merely what developers could achieve given the constraints they had.