Earlier quoted context omitted.
I wouldn't be surprised. I have a gigabit connection and the contract specifically states that they guarantee a maximum throughput of 400Mbit at peak times.
It's like the geico commercials: you could save up to x% on your car insurance if you switch to Geico. It says nothing, there are two weasel word exceptions in there.
So it could save you nothing, or it could save you 15%, or even more. Basically we have no idea what it'll save you, if anything.