The study is irrelevant to the point I am making. The study shows that timber rattle snakes tolerate siblings better. Not that they benefit in anyway or that they seek out their siblings. Even if it did it would not necessarily hold true for other species, especially those as distantly related as BP, and Corns. I am not arguing the points you are making only the conclusions you are drawing.
If an alien were studying me they would assume that I enjoy the company of my brother. After all I call him and he calls me and I go and visit him. One would even conclude that I enjoy my brother more than he enjoys me because I visit him but he does not visit me.
Of course the facts in this study support that conclusion when taken alone. When you consider other facts such as my brothers substance abuse and the fact that he lives with my mother the conclusion changes. Perhaps I tolerate my brothers company because I want to visit my mother. Perhaps I return his calls because it makes my mothers life easier if I do so.
If we all agree that snakes require and thus seek out warmth and security then we can attribute the communal dens to the scarcity of adequate dens.
I conclusive study would have to measure health and stress indicators of snakes housed in identical enclosures with the only difference being that some are house alone and some are house communally. This would have to be done with a relatively large number of animals preferably of similar genetics. It would have to be repeated for each species in question.