The way that quote is worded, each of those could have been separate people/Mantles.
Not how I read it. He was saying that Odin has all those Mantles, and then added that in these days people wear many hats. It's because in the past there were many people with Mantles, and over time those Mantles were consolidated into fewer people, but with more power.
Im not sure what difference you guys are getting at, unless its a question of whether the guy Harry has met is the Original of each/all of those, versus being originally only one (or none) of them and has collected all those the Mantles more recently?
I definitely thing he's saying that a single guy possesses all those Names/Mantles currently. I dont know whether he can combine them, or has to keep them separate as he clearly is doing with the Vadderung/Kringle mantles we've seen in action (ie. Fae one minute, working in a Steel Office the next).
Oh, I agree that Odin has them all, but that suggests that they were separate at one time.
EDIT: Ah, gotcha. I tend to think it's a case by case thing. Some of those I fully expect to have separate origins, the Saint one in particular being something Id expect to need it's own history. But others are, historically, amalgamations that grew out of other myths and/or Mantles. I mean: we have Kringle, Father Christmas, and Sinterklaas, all of which are historically believed to be malagamation myths that (usually) grew out of pre-existing Legends of Odin (usually as the Wanderer). Since Odin has historically had dozens of Names and is one step shy of a full Trickster God, I could easily imagine him spending enough time and/or doing enough Significant (capital S) things that one of his "fake" Names would gain Power all it's own.