I haven't fully figured out how to get it to switch to IPv4, but the reason
you're still getting that IPv6 address is because of a virtual device created
by the IP Helper server. It's an IPv6 over IPv4 tunnel that's on by default.
You can see them if you run ipconfig.

Of course I disabled it, and ipconfig reports no IPv6 addresses anymore, yet
HTTrack now insists on using ::1.

If we had the ability to pick the device and protocol stack for the capture
that would be swell!