It is possible your router supports hair-pinning or (NAT loopback).
When it detects you are trying to access the external IP address (even if it is cg-nat) it is smart enough to router the data basin internally and some are smart enough to apply firewall rules as well…
Simultaneous charge and supply circuits cost a fair bit to design and implement.
It’s a lot cheaper and profitable to build a basic ‘brick’ that can be sold to hundreds of thousands of 'phone users rather than a premium product for a few computer folk.