I'm still not entirely sure why you've been doing what you're doing since it's so obviously not to iTunes' standards. In iTunes, audio is .m4a, .m4p, mp3, .wav, & .aiff, and to a lesser exent, .aa & .
aax (audible formats). In iTunes, video is .mp4, .m4v, and .mov. The file extension .aac has never been supported, which is why the files are ignored until you rename them - the ...