Release candidates aren’t actually betas. With betas, there is an expectation of changes before release; with release candidates, there is a hope that there will be none. In a non-open source environment (ignoring Microsoft’s misuse of betas) both of these would be limited to a selected community.
The assumption is that anyone using pre-releases like this is prepared to override version sequencing rules in packages.
What I would probably question is the release of these as packages at all. I wonder if this is being done by someone other than Digium. From what I gather, most packages are not debug builds, but these really need to be debug builds as they are likely to crash, and they are being made available so that the faults can be found. They shouldn’t be considered suitable for someone who doesn’t know how to collect debugging information.