The only time a GC rider (not a sprinter) might need an 11 is on a descent. They descend on closed roads and can take racing lines comfortably, without worrying about on-coming vehicles. We can't do that, and even if you do spin out, how often are you on the 11? Wouldn't you spend a lot more time on a more useful middle cog? If you spin out your 12, just tuck in and coast.