Ask HN: Why does the US Visa application website do a port-scan of my network?

I have recently installed this extension on FF: https://addons.mozilla.org/en-US/firefox/addon/port-authorit... and yesterday I visited this website: https://ceac.state.gov/genniv/ and I got a notification that the website tried to do a port-scan of my private network.

Is this a common thing? I have just recently installed the extension, so I am not sure if there are a lot of other websites who do it.

Since looking into it, I noticed that uBlock Origin already has the default list "Block Outsider Intrusion into LAN" but it wasn't enabled.