All this means is that they were on the bank of the Nelson at some point. That isn’t surprising as a way to avoid walking, probably with no sense of direction, through dense woods.
Some of us have posited that they could have followed the river, going east or west, along the shore, staying just out of sight.
If they managed to find a boat, the river current runs east to Hudson Bay. Gillam resident Clint Sawchuk takes people there in a 21’ jet boat, distance 145km/90 miles. One of his clients has posted a description, and photos, of the trip. The river is clearly passable going east, indeed quite broad in places as it approaches the ocean, and the client says nothing about rapids. Can anyone add further info on whether there is anything that would complicate passage?
Note that going west by boat would be against the current.