This is more of an aside, but the increase of these flashbacks has occurred at the same time i've been experience worsening tinnitus. The tinnitus is not related to hearing loss, i've been through every number of tests with my ENT. In my case it's almost certainly as a result of something gone screwy in my brain, hyper activity in areas where there shouldn't be (I'm not a brain expert)...

You mentioned that people on the spectrum have more of a tendency to focus on aspects of sound, which is absolutely the case (particularly with my tinnitus). I'm just spit balling here, but having an increased sensitivity to sound might be making my pitch memory more apparent—hence the flashbacks. Who knows.