Going back a few years, if a two seat glider was not available, ie...down for ‘maintenance’, a flight review could be accomplish by instructor/examiner observation from the ground only. I was informed of this in the 1980s by the FAA himself and took it as gospel. Even done a few myself. With social distancing all the rage now, something to ponder.
I would give the examinee a list of maneuvers to be performed over the field, on tow, etc. They had to be current, actively flying. I had to know them and their skill level. 1 high tow, 2 patterns...throw in a downwind landing.
No crash, you pass.
R