Some might be surprised to find out the level of access US border guards have for our personal info as well.
It is what it is. Their sandbox, their rules - anyone who doesn't like their personal info being looked over or scrutinized, well, nobody's forcing you to travel.
And personally, I'd feel reasonably confident that some sort of information sharing system will be put into place specific to vaccination status.
And I'd like to think that the laws around knowingly providing false information would be steep and painful fines and consequences, but knowing the Canadian Government it'll slap Americans providing fake information with a $20 fine, take away their Tim Hortons loyalty points, and send them home all while saying sorry.