Can you share details on how one trivially connects via IPv6 only? I see no option in iOS Wi-Fi settings to do this, and I think it's reasonable to expect not to have to turn off IPv4 on my access point to test IPv6-only networking.

Presumably thats with the network having a PLAT somewhere if you’re relying on CLAT for any v4-only connections when you use safari

I think they're saying you can't force disable ipv4 entirely.