If I had to make a guess, and it's just that, I would say that the fed is looking for a way to actually verify vaccinations from non-Canadians. Here when you register for the vaccine they use your health number. Its similar to a social insurance number in the way that its a government (though in this case provincial not federal) issued card with a number that corresponds to you only and is used every time you access the health care system. I don't know how it works in other provinces but I would suspect its the same. So after you get your vaccination I'm assuming it is tagged to your health number and health records. Since its a government system it should be easier for them to verify if you have been vaccinated. That's the way it should work anyway. Covid is a much more political issue in the US than it is here, though we do have our "special" types here as well. With all the reports of people trying to fake cards excusing them from wearing masks or falsely claiming vaccination it's possible that they want to wait until the majority of the population here are fully vaccinated before they start opening the borders and having to wade through the processes of having to verify peoples claims of vaccination. For the most part I would hope that everyone coming to the border would be honest and follow the rules but since we experienced quite a few US travellers who were suppose to be transiting straight to Alaska but actually went on vacation in various provinces doing touristy things, the government can't take that chance. There's also the scenario that they open the border to fully vaccinated travellers and people who aren't vaccinated at all still show up demanding to be let it because let's be honest, those types of people think they have that privilege and right to do so. Then you have border personnel having to deal with those people instead of letting through legitimate travellers. Somebody might look at that and say "I'm not going to do that" and a lot of the people on here (I hope) wouldn't but the government can't make exceptions. Let's face it, as a group, tourists for the most part are not terribly smart and do dumb things all the time. Ask any park ranger. That'll be the vast majority showing up at the borders. Heck, they were still showing up to the border trying to get in long after it was closed. Unfortunately adventure motorcyclists are a small minority. Although it's entirely possible that that I'm completely wrong. I'm pretty sure that has happened once or twice.