I suspect the Quality scores are a snapshot of customer reports at any moment in time, not a scientific independent measurement. IDNet have a loyal customer base. Whether deserved or not is a judgement.
I've been with them for six years, on a capped line below 40Mbps. I have no gripes with the IDNet network, consistent low latency and reliable for me, but of course the restriction on my OR local loop means I can never take it it anywhere near its potential. That being said there have been periods of packet loss and high latency, which IDNet have been slow to fix it sometimes appears on their network. They seem to have got to grips with it for the time being. But remember they have a large commercial client base, as well as their residential customers, which can put pressure on their network. I'm not sure whether Sky have a commercial client base?
However I have recently found in my experience that IDNet appear reluctant to engage with and argue with OpenReach if there are problems on the local loop. Perhaps it doesn't matter if your line is reliable or you don't push it. Which is my dilemma, why argue if in practical terms it doesn't matter? But we do pay a premium for IDNet; and certainly, in my case, it isn't worth it.
We see things not as they are, but as we are . - Anais Nin