I used the word "theoretically" in the context that I was recreating your theoretical scenario. I confirmed that the reading "would indeed in this case be inaccurate". I'm 100% with you on that, musicmad.
The point was that, practically-speaking, when you turn the knob counter-clockwise "past 0", there's no "-0.0" possibility 'cause the parameter range in this case doesn't cover negative values. Any reasonably-paced left turn past the zero point should therefore result in a "true" value of 0.0, and it's at this point that folks say the Pure Cab™ algorithm is still audible.
Well let's not beat it to death anyway :). On my unit there is a tangible amount of "turn" before 0.0 turns into 0.1 so my money is still on a visible decimals cause of this behaviour.