[mike_d]

It looks like someone technical from your ISP also replied in the comments of your post and offered to set up a call to explain it to you. That is far better than you can expect from almost any other provider.

[thomashabets2]

Yeah, long story short I had a call with him, and he agreed that's probably right but it's not a priority to fix.

I hope they'll fix it soon, but not if it delays IPv6.

If I had a choice of FTTP providers then IPv6 support would weigh really high on my choice, but only one has dug up the street.