I think another way to phrase your proposed measure is:
How many moves could one play as black in a no-komi game against a perfect player before squandering the first move advantage?
I’m not sure if that’s necessarily a good measure of strength. How long one lasts under this criteria may just depend on the timing of when complicated fighting breaks out, or how well one has memorized and understood some key joseki/fuseki.
If we are measuring strength with respect to perfect play, I think a more natural measure would be:
How much handicap (in terms of stones and/or reverse komi) would one need to beat a perfect player?
I think the answers to these two questions would be correlated, but not always directly proportional.