I agree with that. Traders, missionaries, military, outlaws, adventurers and tourists have itchy feet and are not about to stay in one place for long. (I don't believe Jesus did either, between his 12th and ~30th birthdays.)
Just for fun, take a good big map of NW Europe and plot a line in the water around the shoreline about 100 miles out from shore. The Vikings could go that far on a bad day, and double it on a good one.
Then imagine you are sailing in a boat and are fearful of losing sight of shore, or at least for very long. How far is the horizon, maybe 30-50 miles, depending on what's on the shore? Then see how far you can sail without losing sight of shore. It is astounding!
Then imagine you have sailed these waters a lot and are no longer fearful of losing sight of shore for a day or so since you know you can always turn around and come back to known territory. Try hopping from island to island and sail from Bergen Norway to Greenland, via Iceland.
Play with the numbers however you will, you end up concluding that it really wasn't that big a deal for the Vikings to come to America. It certainly wasn't an unreasonable and ridiculous idea. And if you do the same for the Med area, navigating that territory and along the Spanish and French shore to England a thousand or two years earlier is peanuts. (Not drowning might be another story...)
He's postulating that prior to the vikings,Iceland,Greenland,the Maritime Provinces,and parts of the far northeastern United States were settled by a people of Celtic-and Christian-background. Mowatt makes it clear that a long voyage(i.e. Europe to North America)in an open boat without high tech gear of navigational aids isn't nearly as impossible as a lot of people like to think it is.(apologies for the off-topic post,btw)