This is a bit unclear to me, so I'm confirming. When I edit the user that a domain is mapped to, the site is then hosted on the virtual machine that user/admin is assigned to.
I've wanted to rearrange where things are hosted to better organize my domain, but never shuffled admin users about, but am merely confirming I'm correct. A bit of pre-emptive paranoia.
(Too used to working on non-virtual machines I suppose).