Why is the certificate for Wi-Free displayed as being “unsecure”?

"The security of our Wi-Free service is very important to us"

but

"Some devices which use Apple OS and iOS software display a warning stating that it is an untrusted certificate. You can accept this certificate without having any concerns."

Seems like a nice way to deliver your own untrusted certificates to the users of UPC Wi-Free. And "some which" here means "all which."

Also:

https://support-en.upc-cablecom.ch/app/answers/detail/a_id/1...

You can trust we give you security because we say so.