The main fiber network here in Japan (NTT) had the opposite development - their old PPPoE-based IPv4 core network was under-dimensioned for modern traffic patterns, so instead of upgrading it they build the next generation core network on IPv6.

So the first troubleshooting step when someone complains their home internet is slow is to say "have you enabled IPv6 service?"

Switching from PPPoE to IPv4-over-IPv6 means you get switched to CGNAT so if you want to host anything it's a downgrade, but in reward you get far greater performance.