Can two people play Sea of Thieves simultaneously on PC and Xbox with only one copy of the game?

Using a single copy of the game, you cannot log into Sea of Thieves simultaneously from the same account on both Xbox and PC. From the news post about Xbox Play Anywhere on xbox.com:

Can I be signed into the same game on Xbox One and my Windows 10 PC?

At any single point in time, you may only sign into the game on one Xbox One console or one Windows 10 PC. You cannot be signed into the same game on both platforms at the same time.

If you try, you'll receive a message asking if you want to sign out of the other location. On PC:

Using a single copy of the game, you can log into Sea of Thieves simultaneously on both Xbox and PC as long as you use different Xbox accounts.

I verified this with my Xbox Gold account and my spouse's Xbox Silver account. As long as I made sure that the account used on the PC copy was not signed in on the Xbox, we could log in at the same time.

I realize this is not verifiable proof, but both characters in the below screenshot are logged in using a single copy of the game:

I have yet to find any official word on whether this behavior is intended.