In Sweden they crash test vehicles into a simulated moose. A low profile front end will get under the body, the massive moose body then hits the windshield area, and that's a bad outcome for the occupants.
As to a free ride via swimming moose, probably just another tall tale from the land of Paul Bunyan.
I would think the USFS, which oversees the US side of the BWCA, would be very concerned about such activity involving wildlife.
Canoes are not very stable watercraft, easy to tip a canoe and get dunked.
Back in the early 1960's, the BSA canoe travelers did not have a good reputation. Running their aluminum canoes up onto the rocky shores, leaving enduring aluminum streaks on the rocks.
I was there in 1962 at a YMCA camp. Macintosh Lake in Canada is like an infinity pool, the lake is high up, and the surface is the highest point around. What an unforgettable view.