[ska]

Right, that's why I put visa in quotes. And yes, there is no quota but I wasn't clear if there were e.g. COVID related restrictions on application currently.

People have definitely used this for even undergrad co-op, but I don't know how widespread. Obviously more easily applicable for grad students.

Part of the issue is that as you note the admissibility criteria is decided by the border agent you randomly see. So you provide evidence of education and fit for a TN category, but they decide if you qualify, and it's unclear how much guidance they have in this. Appeal process is mostly only through the same agent.

NB: my experience in this area is a bit out of date, things may have changed.