If you measure the change in the distance between the tip of the teeth you will find very little difference between 9, 10 and 11 speed. Even though campy has machined the mounting surfaces of the big ring thinner by .4mm when 10 speed came out and another .6mm when 11 speed came out, the tooth to tooth spacing is NOT that much different. This has been misreported for many years. Someone just meaured the thickness of the mounting area and assmued that it translated into the same change in tooth spacing.

About tooth thickness. I have old steel rings from a 1990 7 speed hybrid bike that are the same thickness as modern 10 speed. 11 speed teeth are about .1mm thinner than 10 speed.