I'm fairly new, and I mostly agree. I always keep score, but I
do come out feeling much better when I strike the ball better (and execute shots the way i
intend
to) with a worse score. Focusing on score alone (especially if not all strokes are properly accounted for), can be misleading for ones improvement.
I think the entire 5-10% you're talking about comes down to luck. Examples of good and bad luck could include: hitting the flag stick, landing in a divot (or other unexpected bad lies), bounces (in general) that could have been
very
different if landed only inches away from where it did, tree ricochet, etc.
I truly believe that the luck balances out over longer periods of time, but not normally in the course of one round. You have your good scoring days and your bad scoring days, and they aren't necessarily reflective of your ball striking/targeting and short game.