I've migrated physical to virtual using the same license without any issues. Several years ago someone at Avaya told me the only difference is the part number that they for tracking purposes, and has a tie back to IPOSS as you don't need Avaya hardware replacement coverage on a virtual server. Not sure if that is true or not but it makes sense. A license for a physical server is a bit cheaper since you're ordering hardware anyway.
I've never tried ordering a physical license to use on a new virtual system, but I can't see how it wouldn't work. One of my migrations was to get off a 6 year old server, the other was a hair on fire exercise where the 9 year old server failed - it was quicker to move to VMWare than wait for a replacement to arrive. All our other SE systems were deployed on VMWare from day one except those two.