Update, I’ve done a thorough shielding job which killed all of the hum when the volume is down. The hum is very prominent with the volume up, which tells me the coils in this pickup are wired in phase. It’s a good thing in that it’ll keep the signal a little more beefy as opposed to out of phase, but it’ll always buzz.
I recommend shielding for everyone who buys this bass regardless of whether you keep the original pickup or not. There is none from the factory and it buzzes really badly as a result.