There is no way they could've ran thru 2 1/2 decades of funk jams to sample, in about 5-6 years.... it's not even possible breh.
20-25 years of music, from 15-20 prominent acts and countless one hit wonders and random cuts all used up in that amount of time? nah.
if you look at most, if not all the dudes who were the most influential in the G Funk sound, they were all in their late teens or early 20's...and we see all types of major/significant shifts in sound from rappers as they hit their mid to late 20's.
G Funk, faded away..cause it wasn't supposed to stay for long.