Have you ever heard of Bedrock Linux? Its an extremely interesting “meta-distro” that let’s you run multiple different distros at the same time only marginally isolated. The whole premise is to merge the systems together instead of separating them with a container style workflow. Tons of stuff works cross distro to! Its extremely cool to have Debian AND Arch packages just installed the normal way on each distro. Its a beautiful and horrifying system, that warms my heart every time I remember it.
Those are distinct distros, while Bedrock is a layer that sits on top of multiple different distros and actively merges them together. At a glance, vanilla doesnt look like they merge/manage other distros at all? So I’m not sure the comparison makes sense. BlendOS is a completely different approach by using containers to isolate the different systems. Bedrock wants to merge the different systems where ever possible. I wouldn’t say either is better or worse as their goals appear to be entirely different.