What are the odds of getting caught on the Mexican Border, 1 in 10 ? 1 in 20 ?
What are the odds of getting caught on the Canadian border with professional forgeries, or documents procured under false names which are NOT on the watch lists ?
Given enough money and resources, do you think you could figure a way in with much less then a 1 in 20 of being snagged ?
What are the chances the forgeries will be caught? What are the chances that the fact name may be a close match to a name on the watch list.
Odds are in their favor, moving across the border and not being scrutinized by professional LEO's.