In New Zealand it is somewhat well known that our local fibre providers actually provisions each connection for slightly more than the agreed speed. E.g. 100mbits is usually provisioned at around 110mbits. So our speed tests are usually just over 100mbits (due to TCP etc overheads taking some of the overprovisoned parts). Wonder if that is what is happening to you.

This seems to fall off at gigabit, but I’d love to test with 2, 4 or 8gbps which Orcon (and maybe others) are offering.

My ONT only supports gigabit out, so I can’t test faster options. That said, fast.com has told me I’m getting 1.2gbps recently…

the common problem with speedtests is that they're all pretty brief. whether it's speedtest.net or fast.com, it's over in a few seconds so they're not necesarily measuring the sustained speed your ISP is giving you, just the burst speed.

that being said, getting a higher burst speed still makes browsing the web a much more pleasant experience, so it's not like they're just gaming the speed tests.

You can't always saturate transfers to and from random servers (whose bandwith is) not controlled by you.