It sounded like entry was exempted from the US if the reason was for an essential purpose and that studying was deemed to be an essential purpose. AIP letters specifically state "While you await a final decision on your application you may commence your studies online". If one is not able to begin classes online due to reasons such as lack of appropriate internet connectivity (one example), and has a residence in Canada (in my particular case, a new residence and lease that began August 1st) I thought this was where Border Agents were using discretion based on the totality of the individual's circumstances?