don't woma pythons have similar adaptations that make them more suited towards sand? I might just set them up in something like Breeders Choice and get a clamshell and fill that with sand for the snake to investigate while out of the enclosure.
No, not at all. Snakes like Kenyan Sand Boas which spend their lives in sand are completely different from Womas. They have very different body shapes, very different scales, a different way of moving their bodies and a completely different way of life. Sand Boas actually do have scales and skin which are adapted to a life spent in sand, Womas do not. Keep in mind that even something like a sand boa does not construct burrows. They move around in dry, loose sand or soil. They don't 'dig' in sand, they more 'swim' in sand. They never make a hole in the ground. They move through dry, loose sand. If they are ever in a burrow it was made by something else.
A lot of people say 'they live in areas with sand, so they should be able to deal with sand'. In reality, a lot of Woma distribution isn't particularly sandy, and while yes, wild Womas do sometimes crawl over sand, they also have the opportunity to get well away from sand whenever they want to. In desolate sandy deserts with nothing but dry sand, you will not find Womas. Again, your 'red desert sand' is collected from the top of sand dunes, and you will never find a Woma at the top of a sand dune. That's not an environment they will ever go to, even though they may live just 10s of metres away from that microhabitat. Actually, you basically find nothing living at the tops of those sand dunes - they deliberately collect sand from lifeless sand dunes because it's the cleanest sand.
A 5' snake in a 4' enclosure with sand all over the bottom is going to be constantly exposed to sand all day every day whether it wants to be or not, which is a very different situation from having access to sand but generally not going near it.
Imagine the argument 'humans naturally tend to live near water and are known to naturally swim, so I am considering keeping my human in a swimming pool with a mattress floating on top for it to sleep on'. Yes, humans do naturally live around water and get in the water, but we will have all sorts of skin and lung problems if we are *constantly* wet and breathing very humid air. We will probably live and be healthy enough for a few days, maybe weeks or even months, but eventually we're probably going to have issues come up. If we weren't able to talk, it might be difficult to explain that this environment is bad for us, and since we seemed okay for a few days or weeks our owner may not realise the wet environment was the problem. If the alien keeping us had never seen wild humans, or had only seen pictures in books of wild humans and they were of humans swimming and playing in water, they may think we were primarily aquatic. I've been to places where Womas come from where there is no sand to be seen, and I'm not aware of any natural Woma environment which entirely consists of dry sand. If you wanted to make a Woma enclosure the size of a large room and one corner was sandy, sure, it wouldn't be a problem, but all else being equal the snake probably wouldn't particularly like that dry sandy corner. If you put a Woma into a pit of sand for a while it will deal with it but it probably won't particularly like it.
Australia doesn't have any particularly well developed sand specialist snakes, especially common in captivity. There are some popular captive options overseas like Kenyan Sand Boas (but as I said, these don't actually burrow either). If you want a reptile which actually does create burrows there are several good gecko options including the good old Nephrurus levis, and if you want something which lives like a sand boa there are some degenerate-limbed skinks which are easy to keep but not particularly common (or all that fun to keep) or you might like to consider Sand Swimmer Skinks (very pretty, fun and easy to keep and pretty widely available).
