You know how nerds who are really into some fandom will pick apart literally any sort of detail in the canon works that's worded weird or contradicts other parts of the canon and concoct elaborate fan theories reconciling stuff? Like ASoIaF nerds with the character who's secretly a horse/transforms into a horse, or minor characters' eyes changing color between books?

Theology is the ur form of that, and the trinity specifically is trying to reconcile the weirdness that resulted from their monotheistic religion originating from a polytheistic one via a henotheistic heresy and the addition of a further aspect of their one god who is ontologically a distinct being from the main one but is also the actual main one but they're the same but they're not and they go around and around in circles trying to explain how the primacy of just some dude who was a guy who said some shit coexists with the primacy of an omniscient all-encompassing universal creator force-being-thing until they just give up and say "they're all the same thing because there's only one of them because textually there's gotta be just one, but they're different from each other, so they're all the core thing but are different things, now shut up and stop arguing about this".

Now is any of that whole question reasonable or normal? No, of course not, it's all very silly nerd shit, like arguing over what Primarch Guilliman's favorite pokemon would be, but medieval theologians - being the only literate people around - didn't have better and more interesting canons like Warhammer lore to argue about so they made do with that.