it's an agreement between those countries. Canada and the US haven't applied to be part of that club yet (probably because of their struggle you provide uniformity QR codes). The issue is on their side.
but I can confirm. I just landed in Bangkok a couple of hours ago and the T8 form wasn't given by the airline attendants neither asked for upon arrival.
No need a special insurance tailored especially for Covid, but you'll need a medical insurance that does NOT exclude Covid. So yes, Covid coverage still needed.