Welcome to our lovely society of bureaucracy nonsense. You've done the right thing. You've contacted all the right departments, and didn't get a clear answer - no one is game enough these days to be held accountable.
I've asked direct questions before about clarification of regulations and acts. They always come back and repeat exactly what the act says - none game enough to interpret, expand or make clear - because it's always up for interpretation by the judge if it goes to court.
Thus requires you to think like a bureaucrat and read between the lines.

If it was not to be treated as a license, it's 'safe' for them to say 'No' - and you would have gotten a clear 'No' answer.
However, if they all understand it that it is fine to be treated as a license, they say "I don't know" because they do know, but because there's 0.0001% of doubt they don't want to be liable. Same response even if it was written directly in the regulations.
Personally, I'd just take the receipt along with some extra photo ID (drivers license) to prove you are you, and be done with it.