Doh! I see what you mean, buuuut I was looking by another section of the rules - last paragraph of the section on retreat. It talks about the chain reaction of a cav retreat, then says:
" If any unit in this chain cannot meet its RETREAT restrictions then the original Cavalry unit must STAND."
So since the art cannot retreat I thought the original cav stands. I have no idea whether this takes precedence or if what you’re referring to does. Let me know what you think.