This doesn't mean necessarily that two snakes shouldn't be kept together.
It means that not enough hides were made available.
Multiple snakes can be housed together - but several things should be considered:
- the species of the snakes involved
- the ages of the snakes
- the size of the enclosure
- the number of hides available in the various thermoregulation zones
There are several species of snakes where breeders and keepers, oftentimes, house them together.
Just because it's easier to house them independently doesn't mean you have to.
Would I recommend housing multiple animals together? No. But not because of some behavioral study that has never been conducted or for the propagation of some internet conventional wisdom. I recommend it only because it is EASIER to house animals singly.