i have just bought an ifixit kit, has some ph and j bits. I’ve looked at them under a microscope, compared angles, tried them on screws... i have found no difference whatsoever, they seem to be identical. What gives?

G-sensor is at least being used for in-ear detection. The bud turns on noise cancellation if both IR proximity sensors are triggered, and the stem is facing roughly downward. Once it’s turned on, the g-sensor is not being used for the purpose, so as to not make the buds turn off when you’re hanging upside down.

Definitely a strain gauge: it is just as squeezable with gloves, tweezers, and possibly anything else.