I just figured when souls, from living or from the dead, are chosen to be given a Ghost, that's the only point in the process they lose memories as they're fundamentally being reborn into a new entity. This new entity, now has the ability to resurrect naturally; natural to a guardian would include a symbiotic like relationship with a piece of machinery interacting with a biological vessel, and this is the system or way the Traveler, a cosmic god like being, simply chose to implement. But now yall talking about pulling bodies out of infinite timelines, never heard of that so whatever, sucks if the new body was just ripped off the toilet or banging some thicc side titan or whatever.