Oops, Apple alert the presence of a bug that might well ruin the lives of macOS Catalina users wishing to install macOS 11.6.4 or macOS 12.3 betas. In this case, the problem is when you try to install these betas on a volume encrypted with FileVault: when you try to reconnect to the previous volume, the Mac might go on an infinite loop of restarts. And nobody wants that.
On the other hand, there is no problem installing macOS betas on a separate APFS volume from a Mac running High Sierra or later, Apple specifies in this help sheet. It is then possible to switch from one system to another.
