Yes a multi-homed PC is a PC that has multiple IP addresses assigned to it. e.g. connected to 2 or more networks.
As for the "If the ESX hosts have IP addresses hard set before first run, then the first run validation pre-checks will fail." I am referring to the first run configuration. This is the steps where you connect to the default 192.168.10.200 IP address and thru the configuration wizard you enter all of the configuration information to set up the VxRail cluster.