Sorry, not being very careful with my words.... Below 10" you just get told "stop" so can't tell between 6", 7", 8"etc...It’s effective resolution is not 10 inches. That’s just the closest an object can be for it to consistently register. It absolutely can distinguish between, for example, 11 and 12 inches.
Of course you'd be sensible to stop at 12", but if it can reliably indicate 11" vs 12" it would be nice it it could keep going down to say 7".
When I typed 'effective resolution 10", I was saying that from the perspective that I don't care about 20", 15" or 12" other than as a rough guide that my eyes can often tell equally well.
It's up close that it makes most difference.