akihmsa, since they allow the .25-20 for Hunters Pistol competition they also allow it for Cowboy PC.
At the beginning the .218 Bee was legal but after the first year or two of competition they determined that some shooters were driving the bullets too fast and were damaging the targets so it was outlawed from Cowboy PC competition. I am not sure what is going on with the .22 Hornet, it may be that nobody is making lever action rifles in that caliber, at least I have not heard of any being made myself.