I played some fast green courses, including ones around 11 or more. I think it was manageable (for me). That was my basis for saying "11 is not that fast." I also practice putting on my kitchen floor and I bet its stimp meter measurement would be higher than any fast green .
Sorry, 11 is quick, but not smoking. I played in a member/guest this past week. Greens were rolled and double cut each day. They were stimped every day and ran consistently 11.5 early in the day. Likely hit 12 by mid-afternoon. That's fast, but not stupid. Augusta will be faster, and of course will have more contour.
I agree though, faster greens are easier to putt, once you're used to them. But, and this is the point of the thread, mid-hcp players that never play on greens faster than 9ish will lose their minds until they get dialed in. And that will take some time. Not just a pre-round 15 minutes on the relatively flat practice green.