A rating of four on the IP rating scale means that the device is protected against debris greater than 1mm (0.039 inches) in size.
That doesn’t sound very impressive. For reference, the raz 40 has an particle protection rating of 5, which means:
Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the safe operation of the equipment.
But the razr 50 dropped that, and now makes no guarantees about particle protection. Folding phone design does not seem to be improving in this area particularly quickly.