First off, I'm pretty new to the forums overall so if this would be better suited for another forum just say the word.

I'm trying to learn Bloom by BTBAM out of the tab book their bass player (Dan Briggs) made for the album it's on. There are a few 16th note runs in the song that I don't think are physically possible to perform (at least, with any sort of cleanliness), and I've listened to the song a lot trying to pick out the bass and he's definitely not playing the fills as they're written in his book.

I have a couple theories here:
1. Dan just sort of slides his left hand up and down the neck while picking 16th notes on his right hand (at least in the studio version), and just found some random way to tab that out.
2. Dan just improvises all these fills (based on the live videos I've found, this seems more likely).

I'm probably just going to ignore the fills written in the book and improvise them, but I want to know if anyone else has an opinion here.