You’re looking at the wrong log line.
The “Access the GUI via the following URL:” line is meant to give the user something clickable, something that can (probably) be copy-pasted into a browser. The wildcard address (0.0.0.0) isn’t routable, you can’t type that as a destination adress. So syncthing will replace that address with something more local (localhost) when creating a printable HTTP URL. It doesn’t neccessarily check whether that assumption is true in your network setup.
Directly above this line, you will see something like this in the log:
GUI and API listening on 0.0.0.0:8384
That’s the actual listen address.