I agree we need C13 greens in stroke play practice rounds. I know we can setup CC tourneys with C13 (even faster) to work out learning. But in practice mode you have the putt preview and mulligan features allowing you to try different approaches to figure things out. It's the same as using the mulligan feature when working out different approach shots to a green having the ability to repeat the shot form the same place over and over.
Also, if C13 can be added I'd love to have C14, C14.5. I'm surprised how different they are from 13.
Have fun and hit 'em straight,