In traditional Morrowind, the golden saints were classified as creatures, meaning you could soul trap them for grand souls. This worked with golden saints you could summon yourself. In Oblivion: Shivering Isles, golden saints were classified as NPCs, meaning they had black souls.
I purchased a scroll of Summon Golden Saint from the enchanter in the Vivec Guild of Mages, I think her name is Janand Maulinie. When I used the scroll, it summoned the Shivering Isles version of the golden saint. I assumed this was going to be the case for all golden saints in Morroblivion.
However, I recently cleared out the Ibar-Dad dungeon, the one on the north coast of the mainland with a treasure trove at the end guarded by powerful daedra. There were two dremora lords, which I killed with a Soul Trap combo spell, but apparently their souls are black like in Oblivion and unlike in vanilla Morrowind. There was a golden saint too, and this one used the Morrowind model, not the Shivering Isles model. I killed it with the same spell, and I did trap its soul in one of my grand soul gems.
Are there supposed to be two types of golden saints in Morroblivion? I assumed it was a glitch, but is it an intended feature? I already noticed that both models of scamps are in the game, with the Oblivion model used for the Creeper NPC, and the Morrowind model used for the enemies / summons.
ETA: I also noticed that this happens with other creatures I've summoned from scrolls. The frost atronach I got from a scroll used the Oblivion model and had its set of abilities, whereas one I encountered in a dungeon used the Morrowind model and had its set of abilities.