Sky will only offer Fibre Max if your guaranteed minimum speed is over 57.4 Mbps.
Wow, that's ... restrictive. Even if they only use they A range. That "guaranteed minium" means that 80% of people will be faster.
How much could the best of that 80% achieve? Well, here's an example...
My previous property was about 375m (line length) from the cabinet, and had attenuation of around 17dB IIRC.
The checker currently gives that line an A range estimate of 59-78, so that line would *only just* qualify for Sky's max service. That checker result means 20% of similar lines are getting faster than 78Mbps!
How did it actually behave?
We got service there when the cab was about 18 months old, so we weren't the first, fresh, crosstalk-free line. We easily achieved 80/20 speeds at first - with attainable speeds of 90Mbps at the beginning.
When we left the property after 3 years, crosstalk had gradually affected us, and the sync speed tended to be 78/20.
It looks like Sky's restriction could be keeping some people with 80/20 capability out of the service.