I don't think this is worth an argument.
I suspect the terminology has a lot to do with what region you are from. Just like midwesterners say "pop" and new englanders say "soda". They are talking about the same thing.
At the end of the day Norway maple is a member of the Acer genus, thus a maple by definition on which we all agree. Whether we choose to call it "hard" or "soft" makes no difference to how it burns and is basically a relative judgement. It is "hard" relative to silver and "soft" relative to sugar.
Regardless of what we call it, as far as I am concerned every Norway maple in america should be cut and burned as fast as possible. The tree is an invasive weed that drowns out our native hardwoods. If we value sugar maple for its BTUs and its delicious maple syrup we should select for sugar maple forests by culling all norways we see. I am on a mission to eliminate it from my land.
For those interested in ID'ing Norways and selecting them out of your forest land, the distinguishing features are:
1) tear a leaf from the branch at the petiole, you'll see a milky sap ooze from the stem. A sugar maple's sap will be much clearer, almost translucent
2) Norway leaves are broader than they are long. Sugar maples tend to be longer than they are broad and are more pointed/jagged looking.
They burn fine. So, heat your house and do the earth a favor at the same time -- cut and split a Norway today!