This is dumb that you wouldn't want as much in put as possible. Samsung just keeps making stupid decisions one after the other about developement and with options, ex Good Lock, Tasker doesnt work anymore with current UI 3.1 but offers many better options to see Recents than the awful Samsung 1 way to see them. I use a Note 20 Ultra, not an iPhone, but at least Apple lets everyone be a beta tester that signs up. Sam acts like it only wants to hear what it wants to hear and not what it needs to hear necaise it seems that Sam knows it's regularly pissing off people with stupid or backwards changes.
Except betas have always been like this for Samsung. It's also not just Samsung that limits betas. There are many software companies that have closed betas that are open enrollment until a limit is reached. Either that, or it's randomized and even if you do sign up, you don't get selected.