The problem with using the iPhone as a compute device to drive AR glasses is the same reason mobile VR failed; battery anxiety.
Article doesn’t really go into the capabilities of glasses though, could be anything from lightweight “smart” glasses to AR glasses and many room in between.
Pretty sure mobile VR (like Samsung Gear VR) failed because putting your phone inside a headset is dumb and adds unnecessary weight... I don't recall many devices tethered to a phone via a cable outside of AR/video glasses; which have not failed. Xreal, Viture, etc. are doing fine and keep releasing new products.
Depending on apple's design goals, they could add a battery to the headset, and/or you can just attach a magsafe battery pack to the phone. Not a major issue compared to AVP which also connects to an external pack for power.