I don't think it is a big of a problem as it looks. Most of the dust / sand issues were on the earlier models and were related to the hinge mechanism itself.

My Fold 4 at some point started making grinding noises that raise ones blood pressure. I guess it is now solved as the new hinges are waterproof and stuff.

The screen does not really fold completely does it? All hinge mechanisms have a way to allow the screen to have a smooth arc on the fold point, not rubbing on itself. I've not used a foldable since that model so these are second hand info.