Anyone can get a $5 bluetooth-capable ESP32 and set its bluetooth mac to one in the range used by smart glasses. Not sure why you'd do that though.

The other direction is trickier. You'd have to modify the firmware of the smart glasses to set a different mac, or at least gain arbitrary code execution with hardware access on the glasses. That's well beyond what the average smart glass user will do

And at that point, it'd be mostly about the heads-up display anyways. Somebody who is determined to record you without your knowledge has far easier paths available to them. Just get one of those lighters or ear-rings or car key fobs with built-in camera

Where does it say that is guaranteed? Nobody can guarantee that.

Are you really worried you might be filmed by an off-brand pair of glasses, instead of a genuine Meta pair?