I have a feeling this, along with gender, environmental, and other proposed clauses, is an attempt by Canada to make an opening bid that's unacceptable to the US, in hopes of using these items as bargaining chips in the negotiations.

I don't think it's going to work for them, but they're kind of in a desperate situation with the US having a lot less to lose if NAFTA falls apart and therefore almost all of the leverage. So Canada might as well try whatever they can.