Nothing is broken, that is the way it works now, and has worked for some time in Safari Technology Preview. I know that assumptions are always risky, but my assumption has been this is security related, but I don't know what the reasoning behind it is. I do know that on some sites in addition to being presented with options "from this site" I have "From iCloud Keychain", encrypted ids from the site I am accessing, and if I go far enough down the list I get to "other passwords" and clicking on that option asks for my userid password to open the Safari password list and you can then choose any password from that list.
