Is assist cutoff point related to the speedometer reading on the Shimano display?

[kylnman]

I'm curious exactly how the processor determines cutoff, and if it's at all tied to the speedometer display. Is it RPM, wheelsize, gps?

 

[KeithR]

Wheel size x wheel RPM, given that pretty much every derestriction technique involves convincing the computer that the wheel is spinning less quickly than it actually is.