Jim begs to differ. He wrote Proven Guilty and then Ghost Story. Your making Merlin's argument in Proven Guilty. And Uriel explicitly explains it at the end of Ghost Story and in Skin Game.
And like time travel or the multiverse or not, Jim has telegraphed how it will work and that he's going to do it.
indeed, it would seem to me he fit in both models, using the idea of conservation of history to double into why history repeats itself.
The mechanism for the actually resetting of time(but not history if that makes sense..) is open to debate,(though stars and stones may have some impact on it, a 2k year timeline has also been hinted at in places, like Woj asking whose in the 'know' like Nic and the answer being beings that have been around for a couple millennia) I prescribe to the gyre theory myself, where in time repeatedly inverts upon itself. So certain events and figures that have cut a deeper groove in time, things with more energy behind them, tend to repeat themselves on the timeline. Which is where we get variations of individuals who resemble each other in deed or stature, events that keep happening, ect.(Woj of Rashid being that last version of Harry and not enjoying it very much)
On the other hand, those beings have free will,(at least now that they're born human mostly?) And the actual manifestation of the timeline itself can vary immensely. Following the Merlinian backdrop I think Harry-Merlin, Marcone-Arthur/Uther, Ms Beckett-Morgana, Hendrix-Lancelot, Murphy was Guinevere, ect.
Course, since time is inverting with each repetition the actual results of each are different.. Murphy's domain was legal not magical, but she ran the other side of Marcones empire, Hendricks died loyal, Marcones a diseased moose Wang, ect. though, I've noticed that the major players on the inside have done things to fill in gaps where things didn't go where they would, either by design or accident. Vadderung took on the position of magical protection for Marcone, and sent Gard to fill the guin archetype, insuring he had a real chance to rise to power in the supernatural world. Gard, who I think was a previous version of Murphy as much as Rashid was Harry, ended up with Hendricks giving light to the Lancelot-Guin love affair, but it didn't cause any problems in this incarnation that I know of.. heck, Denton and co would make a good Questing Beast now that I consider it lol. Iirc he thinned out the knights early incarnation?