Of course they keep them. They aren't deleted, they're delisted so people more easily find the latest one, and don't assume old versions have different content.
Viewing post in Pure Onyx - Alpha Release December 2022 comments
I don't buy that reason at all, since, latest one will be on the top and you can see their month/year to tell anyways, so it is only preventing from checking what people has to say about the builds.
Luckily, there's another site where people are free to discuss and review games so, I am able to know while the animations are great, your history on development has been terrible and scummy.