This is my take on the Rey saber and it's the same as the ESB Luke saber.
We know they used rivets on the d-ring, we have clear evidence of that. This means when they were building the saber they had rivets, a rivet gun, and tools to drill.
Why would they use rivets in the d-ring, but then use screws in the grips? It doesn't make sense.
I can see where maybe the original ESB saber had rivets in the d-ring and ANH style grips that were falling off in the snow and the grips were replaced and they used screws at first. But we have photos of other bladed stunt Graflex sabers from after the production with rivets on the clamp so I feel rivets were the preferred method.
Plus, when doing research the only Graflex saber with screws is the SWR, every other saber available (prop replicas and photos) most likely had rivets as that's what everyone else uses. I would think with the rivets in the d-ring and the available reverence they would have just used rivets.
Plus the Launch Bay sabers use screws, the 'right type' of screws, and it doesn't look like the screen used fasteners from screen shots of the saber.