Being from the Bay and growing up around legendary underground Bay Area rappers, I can tell you Bay rappers sampled hella songs before East Coast rappers did. But you also have to realize a lot of these sampled songs weren’t obscure records. Mtume “Juicy Fruit” was one of the biggest R&B records of the fukking 80’s. They still play that song on classic R&B radio to this day.
Also, a lot of rappers pattern themselves after underground rappers that are relatively unknown in the mainstream. Snoop patterned his early rap style after D-Loc and Richie Rich from 415 from Oakland. But Snoop admits this. He even used the same sample for “Gz and Hustlaz” as 415 did on “Snitches and bytches”. Everybody patterns themselves after somebody. Nas sounds like G Rap mixed with Rakim. Biggie sounds nothing like that B1 dude though.
The only weird coincidence is his name being Notorious B1, him being fat and calling himself big daddy. I know big name rappers with the machine behind them are known to low key steal game from underground rappers. Sort of like how Jay Z said “I got 99 problems but a bytch ain’t one” in 2003 when local Bay Area legend Cellski from my old block in Frisco said that same phrase on “On the Grind” in 94’.