I don't know if this has been released or if I'm in a test group, but I experienced this feature using the cross device template today. Or maybe it's just been added to this one template. It's def nice to have more size flexibility--tbh, I would have settled for even just a few more, especially in the larger sizes where there was SUCH a gap in sizes offered, reminded me of the old editwriters (phototypesetting equipment) if anyone remembers those.
My only complaint is that you have the choice of either typing in the size and clicking to it one point at a time. I would have liked to have a dropdown vs the one-point clicking, but I guess if ALL the sizes are really available, typing in the number is something I could get to remember. It was just an odd feel at first, perhaps because I'm used to a dropdown in this area of the program.