Great question — answering as the UphillTech team:
It is unlikely that any service is going to guarantee that a supervisor is available 100% of the time, and the passage you quote does not claim that it is. Even if it is their intention it might be impossible for many reasons: nobody might be available, or the designated supervisor might be busy with other matters. Speaking with a supervisor is not the only way of addressing any problem you have with CBSA. You can submit complaints and other feedback to CBSA online at this page or by mail, using the process described there. You would need to be reasonably sure that the behaviour of the officer rose to the level needed to make a complaint worthwhile, and that you didn't exacerbate the...
Full answer by DJClayworth: https://travel.stackexchange.com/a/203513 (CC BY-SA 4.0).
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