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.

I wondered about that as well, nowdays with a radios and video cameras moving with pilots head, you might be able to do a pretty good flight review. But it needs good but also legal. The regs in 61.56 and 61.11 provide may some wiggle room (especially for glider pilots) but I'd want to see a letter from the FAA before depending on it. Seems like an SSA of AOPA thing?