Doesn't the grandfather paradox necessarily assume only a single dimension of time? And 1D time leaves no room for decision branching. So it necessarily also as

Doesn't the grandfather paradox necessarily assume only a single dimension of time? And 1D time leaves no room for decision branching. So it necessarily also assumes a lack of free will. Which then gets into an irreducible problem of arguing semantics. But if free will exists, then time must be multidimensional. Multidimensional time agents could then go back and kill their own grandfathers. They'll then be traveling forward in a decision branch that doesn't include their grandfather, but the one that does is untouched. There are other branches where this grandfather doesn't exist, and all people in all those branches would argue the impossibilty of that time agents existing, as he has no path that they can see to get there. But we might as well argue the impossibilty of a coconut showing up in medieval Europe, just because we never saw the swallow that brought it there.