I always thought there were six Dinobots and six Insecticons (not counting the deluxes, just six of the little yellow and purple guys). Not sure why, except possibly with the Constructicons around I just assumed six was the default number for themed teams. I still catch myself doing it, I was thinking not long ago it'd be nice to have Insecticons to go with my Siege Decepticons, but then thinking it'd be unlikely they'd fill up six release spaces over multiple waves just to complete the set.