The inner workings of the X16 does have some similarities to the Commodore PET, an earlier 6502-based system from 1977. I recalled Dave's Garage did a segment a while back describing some of those aspects. Here is the specific offset a few minutes into that video discussion:
EDIT: yt tag doesn't like time index offsets. Interesting stuff starts at 6min 42sec (t=402s)
Towards the end is notes on the FAC (floating point accumulator), and there is a brief note on what address the 6502 uses to know where to start the system. This just touches the surface about the system, but it might be a useful intro to those new to systems like this.