Interesting–I just got a pair of the RXLs (in size XL) and the ankle hole was just right. I never thought of myself as having particularly large ankles.
I’ve been using the Pearl Izumi Elite Barrier bootie for the past couple of winters and I’ve been pretty happy with them. The XL size is a snug fit for my 46 shoes, but they’ve kept my feet pretty warm down to about 25°. I still miss my old Performance Booties from before the line was redesigned several years ago.