Unlimited Data no longer available with customer owned DOCSIS modem?!?!

I have a friend that is near their data limit for the month.  They currently use their own DOCSIS modem for connecting to the Internet via Comcast and wish to continue to do so.

When contacting Comcast Customer service, they were told the Unlimited Data option is no longer available and has been replaced by xFi Complete.  Customer service was very insistent that xFi Complete had to be purchased and that Unlimited Data is not available any other way.

The information I can find on Comcast's website is not consistent with what Comcast Customer service states.  What I found is this:

https://www.xfinity.com/learn/internet-service/xfi-complete

This web page lists Unlimited Data with "Your Own Equipment" as being it's own seperate thing.  Based on the information on this web page, xFi Complete replaces the customer owned equipment.

Which is correct?  The Xfinity website or Comcast Customer service?

If the website is correct, why is Comcast Customer service outright refusing a request to sign up for Unlimited Data as requested by the customer?

If Comcast Customer service is correct, why hasn't the webpage been updated to be consistent with what customer service has stated?