Canadian border patrol is chock full of assholes who literally have unlimited power and little to no oversight. They choose what they want to do based on how they feel.

CBSA is generally better than the CBP on average, but there is still a contingent of racist assholes within their ranks.

The treatment in Canada isn’t as bad, but the punishment is carried out by the US if a Canadian officer is having a bad day. I tend to give the benefit of doubt where it’s warranted like this case.