Goldie mentioned it previously
but i think the thought from Knock Twice seems to be that Dre is more of a composer than a traditional producer
I know i know, its splitting hairs
but people bring up Quincy Jones, who composed the thriller album and others. He might not have played a single instrument, but his involvement was extremely vital to the success and composition of the songs/albums. Thats not a discredit to Quincy or Dre b/c they ultimately have the vision of the project.
traditionally, or at least in rap, the producer was thought to be the guy who actually sat down with the drumpads, keyboards, etc...and composed the beat from start to finish. May have had a team or a guy or two who might've played an instrument or something, but the main guy ultimately got credit or rather recognition for the creation.
Goldie and everybody agreeing with him are thinking of Dre as Quincy. Knock is saying that b/c Dre didnt create original guitar riffs or melodies that he got from other albums, that mannie is better b/c a huge percentage of his work was all original compositions up until he sampled for the first time many years later