I have no skin in this game but the most common answer to this is that it's a lot easier to tell when someone is pointing a phone at you, unless they're REALLY being sneaky. With glasses this becomes impossible.
What are you supposed to do with this information though? Ok, so now you know that you're being recorded (presumably in a public place) - what's the next move, and how does it bring about a result that is practically different to you never being aware of the recording?
I can concede the case of 1-on-1 interactions, where a smartphone is much more noticeable than smart glasses, but IMO the march towards AR glasses is inevitable. Eventually we'll get to a point where either people will be able to recognize smart glasses in those situations based off of prior experience, or indicators to distinguish smart glasses become standardized.