Is it just me or is there some general confusion in the drummer community about rhythmic devices such as polymeters, modulation, polyrhythms and such?
There isn't much confusion among trained musicians, but drum set players with this level of education are pretty rare. Drummers with "street" training treat musical terminology in much the same way rappers treat language. Nothing wrong with that, of course, but as an educational resource, it's less than ideal.
I have noticed that, among drummers with such training, "implied metric modulation" and "metric modulation" are often interchanged. As TB points out, metric modulation results in a tempo change, where as implied metric modulation reverts back to the original tempo at some point. Gavin Harrison's Rhythmic Illusions discusses this at length, and he leaves out the "implied" part of the term. Oh well.
In your example, there most definitely is a metric modulation. If I understand you correctly, the 8th note triplet becomes a 16th note, and your new tempo is 90 X 3/4 = 67.5 bpm. Because you are playing 3 beats in the space of 4 beats, you could argue that there is a polyrhythm (or cross rhythm) happening in each measure, although, typically, polyrhythms occur when BOTH rhythms are being played at once, and it sounds like you are first playing one, and then other other, and not both at the same time.