Xfinity Streaming App Does Not Work On Streaming Devices Connected to Non-Comcast Network (e.g., AT&T Fiber)

I currently have both Xfinity Cable and Internet services from Comcast.  I have cable boxes for 2 TVs, but I am using Roku devices connected via WiFi on 5 other TVs to stream content using the Xfinity Streaming App (on the Roku).  This allows me to stream both Xfinity content and any recorded programs on the Xfinity DVR connected to my main TV.  It all works great!

I recently installed AT&T fiber for home Internet (better Internet service at a lower price point) and I kept my Comcast Internet just until I was sure everything was working.
I started switching all my devices over to the new WiFi network, but was VERY DISAPPOINTED to find that the Xfinity App would no longer work on my on my Roku and it displayed the message "This device can only access Xfinity Stream on your in-home Xfinity WiFi...".

I have researched this and I believe that Comcast does not allow the Xfinity Streaming App to work on devices that are not connected to a Comcast Xfinity Network (in my case specifically Roku devices running the Xfinity Streaming App connected over WiFi to my AT&T fiber network).  NOTE:  Smart phones and other mobile devices connecting through wireless phone networks have similar limitations but they do work on a limited basis (some content cannot be accessed but other content can).

Is this correct?

NOTE TO COMCAST/XFINITY MANAGEMENT
Assuming that I am correct with the above, I would like to share my perspective on this with you as follows:

I have been a Comcast client since 1996 (starting with the original beta-testing of broadband Internet over cable in Arlington Heights with the original @Home network).

I decided to install to AT&T fiber for my Internet service because that technology is better (i.e., I get better service at a lower cost) - Comcast/Xfinity does not offer direct to home fiber connectivity in my area - if they did, I would quickly switch to that service and this would not be an issue.

I decided to replace the basic cable boxes on 5 of my TVs because Comcast charges $10/month per box (these same boxes used to be about$5.00/month per box).  Since I do not watch these TV's very often, I replaced these boxes with Roku devices (at $30 each) and am now saving about $600 per year.

I enjoy the TV service and offerings that Comcast/Xfinity provide and would like to keep my service.

However, unless there is a solution to the issue I listed above, I am encouraged to explore other TV services (YouTube TV, Direct TV, Streaming, etc.) to replace my Comcast TV service.  In which case, I would then terminate all my Comcast services.

Since I am paying for the Comcast Cable TV Service, my expectation is that you should allow me to access this content on all the TV's within my home (at a reasonable price).  Possible solutions include 1) Lowering the cost of basic cable boxes for additional TVs, or 2) Allowing the Xfinity Streaming App to work on non-Xfinity networks.  Hopefully, you will consider one of these options.

Sincerely, A long time loyal Comcast customer!