It works something like this: Core developers would rather work on core bugs and features than chase bugs introduced by 3rd party components. Just telling people not to install components obviously wouldn't work.

Also, the SDK may change in not-neccessarily-forseen ways during the pre-release process, causing additional 3rd party bugs were open development allowed.
Certain privileged components with strong ties to the core are given access to the pre-release SDK so that they can work with the new system, provide feedback and suggestions to the core developers, and supply such core components for beta testing. After all, who would seriously stress the beta if all it could do was play standard inputs?
As long as the plugins you have requested have not been abandoned by their respected authors, they will be updated in turn. When this is isn't known and asking will only result in having the thread shot down and locked as someone helpfully demonstrated just today (for umpteenth time).
If you really need 3rd party components for your audio enjoyment, it is recommended that you stick to the official release. However, if you can live without them, use the beta and contribute by explicitly detailing any bugs you may find. And remember: "Good things take time."