The H2 Chip uses even less power than the S11 Watch chip.
Watch OS. If there is no screen what is upside of WatchOS? The HomePod Mni runs a variant of tvOS (if I recall correctly). If all the glasses are doing is audio (in/out) and perhaps pushing down camera output then it is far closer to the firmware that the AirPods run. Extremely little computation means don't really need a relatively large and/or complicated OS either.
[ The HomePod could have a smaller OS than tvOS but I suspect Apple is eventually heading towards something like the Amazon "Show" Screen+Speakers 'smart' device. the Micro display on the mini doesn't need much. It is also likely cheaper for tv and homepod line to 'share' the OS cost overhead over a higher aggregate unit volume also. ]
Hard to do 'visual AI' when have no screen. If mean camera capture computational AI. A mini (or micro) R1 may be a better fit if just have pure "camera RAW" processing issue.
The Watch has gyroscopes. There is reduced need to measure signals to the muscles if can feel the motions produced by the muscles. (e.g, Watch already has a pinch to do X , raise to wake , etc. )
If just did orchestration then Glasses + Airpod + Watch (+ Phone) required as a combo would lower the load on he glasses a substantial amount ( wouldn't have to do audio in/out either).
If sperad the batteries around ( AirPod , Watch , Glasses ) then don't need to be as swappable. Watch and AirPods work without swappable.
The in-ear AirPods already provide audio privacy.