Jim,
By "bad stroke" I really meant to be more inclusive. I should have said "an error by the golfer". I know when I switched from the public course where I learned to play to a private club with very, very well-conditioned greens it became obvious when I was having a good putting day and when I was having a bad putting day.
With slow, bumpy, grainy greens probably stimping 5.5-7 in the summer and 8-9 with winter poa triv overseed I could occasionally ram in a 10-footer but most of the time it was Brownian motion from putter to hole over that range. With faster, true, semi-grainy hybrid greens stimping 10-10.5 year round at the private club I'd have days where everything inside six feet was automatic and other days where a poor stroke on a 10-footer could easily leave 5, 6, 7 feet for the next putt.
It's a whole different game fast, true greens.