If this were true, the tests would be conducted anonymously. Or if not anonymous they could at least defer to provincial isolation restrictions rather than enforce a 10-day isolation from the date of the test.
If this were true they would only allow swabs that could be collected for detailed analysis. The quasi-self tests you do at home with a nurse on video link can’t detect and report on which variant you have.
If this were true they wouldn’t allow an exemption because you had a positive case 6 months ago, which doesn’t rule out you getting it again, and certainly doesn’t rule out you getting a new variant, which this broken system is apparently designed to monitor.
The government intention with the random arrival testing it to gather statistics. That's what the government says, and that's also the only reasonable explanation. I'm not saying that I support this, or that it's a smart or efficient method to gather survailance about incoming variants.
I agree that there are many issues with the way they implemented this as well. You have to realize that this random selection is sort of inherited some aspect from previous policies, when they wanted to test all incoming travelers, during the initial Omicron wave, to stop the spread of the disease. Back then, it made sense to quarantine travelers with positive results, and I think the requirement today is a leftover from that time.
Regarding your comment on variant sequencing, I think you are mistaken, as the swab is sent to the lab, which performs a the PCR test, and is able to also perform genetic sequencing to identify the specific variant.