I would hesitate to call this a mapfelwine...I'll bet you get very precious little (read: probably none) maple flavor from adding a quart in a 5 gal batch. I'll admit I've never brewed or tasted that particular recipe, but I've used maple syrup in brewing before, and it's a pretty subtle flavor. I would be more inclined to ferment everything else separately, then add the maple syrup after the primary fermentation slows down. If you do plan on bottling/bottle conditioning, you can also consider priming with maple syrup.
I've read that Grade B syrup has a stronger flavor...I've only brewed with Grade A because it's more available, but I plan on trying Grade B in one of my recipes when I can get a hold of some.