I think the problem was that students need to also have a smartphone or something available during the test for questions and announcements or something, since

I think the problem was that students need to also have a smartphone or something available during the test for questions and announcements or something, since the software locks down the testing computer. And there was no way to prevent people from looking stuff up there. Anyway, once they do impose this requirement to not access canvas, a cheater would just make it available offline. Ultimately the way professors spot cheaters is in their patterns of answers.