> I'd personally like my Starlink to use its real GPS for calculating which satellites it needs to talk to, but only report a truncated (or no) location to HQ, so that SpaceX doesn't have my meter-resolution location every time I'm online.

That’s actually what it does by default. Unless specifically activated for debugging reasons, the terminal does not send its lat/lon, so the most they know is what cell you are in (~10km-ish resolution)