Do not assume the Kringle Mantle is the same as other Mantles. I suspect there is only one day per year where he cannot but be Kringle but has more latitude the rest of the year. This isn’t the same for the Faerie Mantles.
Yes, Uriel has been in on the conspiracy since Grave Peril. The choice THIS Harry took opened up possibilities that didn’t previously exist, and note Michael was present when this decision was made, Uriels agent. Harry’s choice? to try to save both Michael and Susan even unto his own death. It’s the next book Summer Knight Mab turns up and starts showing interest in Harry, prior to this Harry wasn’t on Mab’s radar, only Lea. Michael knew about the coin, obviously so did Uriel and it opened up the gift of Soulfire. They had always intended for Harry to get the power ups of the Mantle and Soulfire, they didn’t plan for Demonreach, that was all pure Harry, stepping in it and coming up smelling of roses although that proved to be essential in surviving Changes and Battle Ground. Together with Vadderung and Hades they planned to transfer the Superweapons to Harry, another power up.
With Harry it isn’t all predestination he has defied prophecy, entropy and death curses, and lived through them all, I think as a Starborn that is part of what he is, and the Spear magnifies that I think, from the personal to the global. Without it he can break prophecy applying specifically to him, with it he can break prophecy applying to the whole world. He is Nostradamus bane.