That is correct. I have done it, not exactly with that hub, but a flip flop BMX hub, running a metric 15t ACS (not AC) freewheel on the small side and normal English threaded freewheels (16,17,18,20) on the other side. The hub is on my offroad SS, and I use the bigger freewheels for offroad and flip it over to the 15t when I end up riding that bike on the road or on a very easy trail. However, as helicomatic noted above, 22t-13t is a huge difference, and I'm not sure you can do it without also changing chains or removing/adding links. But you could very easily run more closely spaced pair of metric and english freewheels with a BMX flipflop, provided the axle was properly spaced.