I guess they back either other up. Like archive.is is able to take archives from archive.org but the saved page reflects the original URL and the original archiving time from the wayback machine (though it also notes the URL used from wayback itself plus the time they got archived it from wayback).
So I just answered my own question. I was confused by this,
Because I thought the Safe Third Country Agreement allowed them to be sent back with no right to be heard for asylum (unless they stuck in and evaded detection for 14 days).
However, according to https://www.wilsoncenter.org/blog-post/safe-third-country-agreement-expansion-causes-asylum-seekers-explore-new-routes
So I guess to get into Canada they’d leave the US and fly in from another country somehow.