Foremost, big kudos and respect that you have driven this across the finish line so diligently and persistent. Chapeau!
For all your questions about the inner workings, I do not feel myself in a position to participate in any meaningful way.
Just one comment:
Does this align with Kevin’s development goals, in particular the rework of the probing and homing commands?
Your explanations sound as if the described concepts could (should?) be carried over to a broader scope, e.g. probing in general (agnostic of the probe type) or even sensorless homing (strange name anyway, since it uses the stepper driver as sensor).