EDIT: I'm not sure, this article says it can detect spaghetti just from the pressure difference, for example:
https://all3dp.com/1/nextruder-prusa-xl-deep-dive/
It also hints at detection of the height while printing.
They currently only use the load cells for bed leveling: https://www.youtube.com/watch?v=F7ETSVu04ao&t=940s
I could be wrong, but I would expect that the load cell readings would be far too noisy in order to determine the height of the nozzle while printing. Even if they were accurate, different materials would also behave differently due to different viscosities.