The ONT can still have an IP address independent of pass-through mode; this is often done so the ONT can be remotely trouble shooted by the ISP, although if they’re burning a public IPv4 address to do this… that’s just wasteful.
As for CGNAT, I think what matters is whether other hosts on the Internet can see the address your router has configured. I like to check wtfismyip.com
Traceroute has some known deficiencies, or rather it is often used for things it wasn’t meant for, so I wouldn’t necessarily put too much concern behind what it reports for the intermediate routers. If you’ve got a pubic IP address and it behaves like one to your applications, then you should be good to go.