There's no contradiction. Two things are happening here.
Foreigners in the US (H1B applicants) are heading up to Canada because the immigration policies are more lax.
Canadian citizens from Canada are heading down to the US because the salaries are higher, and under NAFTA Canadian engineers qualify for an easy-to-get instant visa (TN status).
Foreigners in the US (H1B applicants) are heading up to Canada because the immigration policies are more lax.
Canadian citizens from Canada are heading down to the US because the salaries are higher, and under NAFTA Canadian engineers qualify for an easy-to-get instant visa (TN status).