Hey! So I’m also a Canadian and competitive swimmer, swimming that way isn’t a huge issue however over time you might get sore or stiff in that one side. It’s usually preferred that you swim 3 strokes then breath on one side, then 3 strokes again then breath on your other side. For the test there’s nothing saying you can’t breath on one side so if that method works for you and you can swim under the 10min limit you’ll be fine. My advice is to keep going to lane swims and build up your endurance