I cant comment on housing snakes together from personal experience, But with any reptile, The only benifit is saving space and money, which in that case, I would not say the person should own the animal if they want to take shortcuts. Save space by keeping tubs stacked, or a rack, not endangering or stressing the animal.

But with sand, Heres the deal why Sand, but calci-sand more specifically is bad for all reptiles. Anyone with it, take a little bit, ad a drop or two of water. And tell me what you get. For those that wont do this or dont have calci-sand, It turns to a rock, Its called Cal-crete, and is used in rural africa and other areas as roads, So you are in essense putting cement in the animals body if any is consumed. You wouldnt eat cement, Would you make your pet? Also the calcium draws them to it. It could stick to mice, (and insects for beardie matters), and would probably be messy. A wet/moist snake (comming out of a moist hide, the vent after defication) this could get sand stuck easy.

Anyway, Sand has no place for a ball python IN MY OPINION, along with housing together for non breeding/ short term purposes. But i would not use sand, and also take out the calci-sand in your dragons enclosure, At least replace with childrens playsand which does not clump into cement. \

Ben