Is it possible to avoid a tenant migration by upgrading all existing licensing on the commercial tenant to GCC prior to activating the GCC trial?

The GCC eligibility confirmation letter states:

Please note:

· Commercial O365 licenses and O365 GCC licenses cannot both be assigned to the same tenant. If you have an existing tenant that has Commercial O365 licenses associated to it, you will need to create a new tenant using a different domain for your O365 GCC licenses.

· If you have an existing tenant with only O365 GCC licenses, you can activate this trial for your existing tenant. Please use a real tenant name as you will be able to purchase directly via the trial.

I suspect GCC licenses can't be added to a commercial tenant which would mean a migration to a new GCC tenant is required.

Thanks in advance!