I was surprised to read that the total area of the Old Course greens is 6.1 acres, considering that the 14th/4th double green is reputed to be over 1 acre. This would leave about 5 acres for the other 10 greens, or which 6 are double greens.
If, as has been said in previous posts, the greens at Old Mac have just been extended by cutting a little further beyond the original green limits - for example the aprons, then it seems reasonable enough. What I would not like to see is very large greens where the green extensions were considered for pin positions.
My home course, Bro-Bĺlsta has the largest greens I've ever seen. A number of them are 55 yards in depth, with widths of about 30 yards. I feel a little deprived when I play this course, as some of my (many) miss-hit wayward shots end up on the green. You might say "that's great", but in my opinion, thes miss-hits shouldn't end up on the green. It is more enjoyable to have a difficult chip or putt - up a bank or from a hollow - back to the hole, instead of a 90-100 foot putt.
It's nice to have an opportunity to use your putter from off the green. I have seen some players using the putter from up to 100 yards. Some people may scoff at the thought, but in many situations, it's the right club to choose.
Dónal.