My understanding is that this is just the OS trying to fetch a known page over HTTP and, if redirected, assuming it got a login portal and presenting it to the

My understanding is that this is just the OS trying to fetch a known page over HTTP and, if redirected, assuming it got a login portal and presenting it to the user. I assume this can continue "working" (with your noted caveat that it doesn't even always work today) forever, as the process that checks doesn't need to understand HSTS or to ever try HTTPS, regardless of what actual web browsers start doing.