I wouldn't consider it cheating. What we use as notes are really just sounds and tones at certain specified frequencies. What you're doing is calibrating your ears and mind to save and recall particular ones, that's all.
You could sing or play every note at +15 cents sharp and still technically have "perfect pitch" because all the intervals are relative to one another even though it is not within the standardized A440. That person could sound great by themselves but would struggle to play with others as their brain would have to be constantly making the adjustment of -15 cents to what they would normally hear in their head as that had been established as their standard over time with repetition. To that person everything we would play would probably sound flat.
For guitarists it's easy to transpose because we can tune to that sort of thing and everything remains in it's familiar place. This is why we have capos as well. We don't care what key it's in as long as we can play something our muscle memory is familiar with. Keyboardists have it real easy as they just hit their little transpose button, I mean wow... I guess it wasn't enough that your instrument was perfectly in tune EVERY TIME you go to play it, lucky bastards.
Singers on the other hand, have to train and maintain their ear, mind and voices non stop or you can get rusty in a fairly short amount of time. I guess the lesson point I'm trying to make here is to start the discipline of doing everything musical in tune as early and as consistently possible because it can only help you. Seems to me like you're doing it.