declarative host_vars config is confusing

[davidmnoriega]

This statement in the readme about host_vars does not make sense, "The vagrant-compose plugin allows to define one or more host_vars generator for each ansible_groups." Why are host_vars keyed off of group names? How am I supposed to set var1=alpha for hostA and var1=beta for hostB? Right now this works in one environment because the host I want to set host_vars for is the only member of the group.