A proficiency check is conducted to renew or revalidate a rating, and does not require a licensed airfield
That's how I interpret rules but
becoming qualified for
the grant of a pilot’s licence or the inclusion of an aircraft rating,
It does depend on whether "inclusion" means only Initial Test (so that Rating can be included for first time) or also means
subsequent Revalidation/Renewal Tests (so that Rating can continue to be included)