I would not go so far as to call a ball python arboreal or even call them tree dwellers. I think ball pythons will climb on things as they are cruising through the savannah. It is not like they will come across a shrub or tree and think "I need to find another way around or I may fall if I climb up that thing". The fact is they can live long and healthy lives on the ground in tubs and cages. Adding enrichment items like branches and vines and other things to climb just helps to give them options to scoot around but going so far as adding or inferring the word "need" into the equation might be a bit of a stretch. Finding something somewhere does not mean it lives in that location.

Let's take my rosy boa for example. They are ground and crevice dwelling snakes as shown from years of scientific research and the desert like conditions (chaparral actually) they live in. When I pick mine up, aside from trying to bite me because he is crazy food driven, he climbs. Should I now assume he must be a tree climbing snake? Nope, do I provide him things in his cage to climb and did I observe him climbing to the lip of the top of the cage when I got him? Yes.

There are more than just trees in these snakes habitats and they will climb over. in, around, and through them. Termite mounds for example are pretty tall and they need often to climb up to find an opening. Let's not call these snakes semi arboreal as they simply are not physically designed for it. They are terrestrial snakes but even terrestrial snake can climb. You want to see an arboreal snake, check out a green tree python, carpet python, or certain rat snakes.

Let's admit enrichment items are a beneficial bonus but not something that withholding is going to lead to anxiety or depression as seen in other animals like dogs.