I've heard this referred to as being "proud cut" my understanding is they don't remove all the tissue therefore they still act very studdy but cannot impregnate a mare. I know a lot of ranchers prefer theirs this way due to stamina etc without worrying about accidental breedings, however they will still mount a mare and can be very VERY difficult during breeding season so I see it as being pointless and dangerous. The first horse we owned was proud cut, I took him to the vet to have him gelded not knowing any better I thought ok job done...boy was I wrong, When we got our 2nd horse a filly he became very aggressive, would mount her, chase people across the pasture flip his butt around like he was going to kick an all around butthead! Needless to say I called my vet and asked him all he said was "we do all our geldings that way" Ugh I told him well I can't keep a horse that is unsafe around my kids so he was sold. Later we had another gelding pretty much same situation although he had already been gelded we only kept him a couple days and I took him back to the original owner. Since then I've learned ALOT lol the last gelding we had was incredible he was a true gelding and very good with the mares never gave us any trouble whatsoever. Then someone stole him( grrrr ) We don't have good luck with geldings LOL
Theres a high posibialty that he is proud cut... like still has one teste left... if that's true then he might be able to breed a mare... but I have a gelding and he still acts like he's a stallion, but he is deffinatly not. Its just his personallty. I would ask a diffrent vet to check it out, see if he's proud cut.