I've read interviews with Tip where he says that producers were typically seen as crews instead of individuals. He specifically pointed to the Trackmasters and how he wanted to be part of a crew like that which made him less insistent on getting credit. And look at all the other acts leading up to Tribe....there are all sorts of unclaimed or unclear producer credit situations. I just always assumed the dj's made the beats during those years....so Eric B made Rakim's beats, Ali made Tribe beats, etc. Obviously I was very wrong but noone really seemed to care to make that shit clear back then. And you're right...the emergence of Pete Rock, Primo, et al becoming stars just for production work probably changed all that.