I don't pay enough attention to it, but I never hear Canadians complain about the quality of Cubans. I'm one of the only people I know up here who even attempts to buy NC. I never hear my friends complain of a poor quality cuban.
I wonder if online retailers intentionally move lower quality sticks in boxes bound for US, as they know you might be more willing to accept it considering its contraband, and a reliable source that gets you the product. Where here, and other places there are more avenues to obtain it, therefore we may not tolerate receiving a box with bad sticks in them, and won't go back to that source.
Of course that theory goes out the window if the boxes the US gets are still factory sealed.