I was referring to this part that was related to me by a friend, and I reckon we both misread it and misunderstood it (neither of us native speakers of English):
3. Get your COVID-19 test document validated before getting to the airport
During online check-in, upload your test result document, or use your camera equipped mobile or tablet to scan the QR Code provided on your test results when prompted to get it validated. Taking advantage of this option will help speed up your airport process.
Note that this may not be available on all routes.
You can upload your document or scan your QR code when check‑in opens 24 hours before your flight, and up to 6 hours before your flight.
But from this we understood that if the result comes out less than 6 hours before the flight, then it can’t be uploaded. Also, both my friend and I are US citizens and not Canadians. Don’t know if that changes things in terms of that particular requirement being overlooked or what.