Which is perfectly valid usage. CGNAT addresses are supposed to be used on ISP-customer link. Whether there is customer router or just customer end computer on that link is customer decision.
The phone carrier situation is similar - CGNAT address is assigned to customer device on radio interface, whether that device is phone or LTE-based router is customer decision.
We have unfortunately discovered phone carriers who hang out cgnat addresses directly to phones, so we will need to do something else there.