This doesn't make sense to me. Orlondi is in no way special compared to other vampire royalty, or anything. We have no reason to assume his intrinsic physiology is in some way different, whereas someone like Fraudrin has actually displayed numerous unique traits (like jumping from bodies at will).
But I will say that I've always been suspicious of the feat itself.
Vampires explicitly can't regenerate from decapitation or
dismemberment (also being reduced to a
charred corpse, but that might be a special case). For example, one member of the Royalty is
killed when his lower body is crushed, albeit
after some time. Yet Gelda was able to
regenerate and survive decapitation because DK's blood strengthened her.
Orlondi had just been
snacking on tons of blood from Ban, who's regenerated from body destruction on numerous occasions. Additionally,
Ban's blood can heal injuries even without Vampiric powers. After that, Orlondi was
taken as Merlin's spy and
physically transformed into this abomination.
So, I think the more obvious conclusion is that vampires normally can't survive this level of injury (as I showed with Gan crushing Mod), but Orlondi had been strengthened by Ban's blood.