You have no basis for your first opinion. The photo shown is from top-down, so it is unknown how thick the arms of the glasses are. More room for batteries than Apple Watch. But more importantly, we don't know what work these glasses have to do. At a minimum the glasses' SOC would need to handle networking, paint/project some pixels, and drive sensor(s) - e.g. a LiDAR sensor like what's on the iPhone 12. Those functions don't require that much energy and should allow the glasses to last all day. All computationally intensive tasks (e.g. AR rendering) will, no doubt, be done on the iPhone.