I had a samiliar issue a while back, a buddy of mine had a 182 wich is HP, I decided to get the HP endorsment just to be on the safe side. 1 hour ground and a quick flight with a couple touch and goes and got my endorsement.
I used to look at it that way too, same "cat and class".. But just so I dont have to worry about it. It looks like if you start logging time, it'll prob be on the back of your head without that endorsement..