I would not have massive concerns about cleaning it would be not much worse than newspaper. Change the whole thing wash it in boiling water and let dry and then re-use. humidity is not a problem either humid hides solve that too. I am not advocating however!

My concern is much more serious, accidental ingestion. One bit here and there might not be an issue but sometimes things go wrong and a poor strike or a broken open rat could lead to large amounts being swallowed. Not a single few stones but a number. I know from experience what a mouth full of cyprus can cause (yes it is rare but I had it happen) a solid indigestible lump it won't pass and won't move.

I don't see any benefits to using stone over anything else, it is costly to replace and it will need to be every now and again. The downsides of likely higher chances of digestive issues to my mind makes it a higher risk substrate (I do not believe there is any that are without issues) There are simply better options.

The photo is deceiving as it came from a breeders site that if you look over it that same rock and plant and show up in many other photos I am 90% certain this is a set and nothing more. Someone should write the breeder and ask to be certain but to my mind it is a photo set.