A lot of what makes a humbucker a humbucker, a strat pickup a strat pickup, and a P90 a P90 is in the construction. If the pole pieces are magnets, it has the chime like a strat, bar magnet underneath, humbucker, and the split magnet on the bottom is the P90. Be aware that these are broad strokes I am painting with, but those configurations color the pickups considerably in those ways. I have a P90 and T90 that can be put in series, and it is not a humbucker in the classic humbucker sound. It isn't bad, or muddy, but it is not a humbucker sound.
Patrick