Did anyone every answer you offline ... I am installing second hub (Insteon) and Alexa device ... initially for the same reason. I'm going to bet this is a "feature request" for Alexa as they would have to put that ability in. Seems easy enough though ... since we can give the Insteon hubs different accounts, and rooms different names .. shouldn't be that difficult.
At this time, though I bet requires a second smartphone setup with alexa app.