Xfinity Stream App Data Usage

I have done 2 Chats around data usage for the Stream App. I was told (2 chats, 4 people) that using the Stream App will use up the data that I get (1.2 TB plan).  However your website FAQ says this: 

Will live TV and/or Xfinity On Demand streaming on the Xfinity Stream app or Xfinity Stream portal count against my Xfinity Internet data usage plan?
When you're in your home and connected to your in-home Xfinity network, streaming video to the Xfinity Stream app and portal is an in-home cable service delivered over Comcast's managed cable network, not over the Internet, so it will not count towards your Xfinity Internet monthly data usage. If you watch any TVE content through Xfinity Stream, that programming is delivered over an Internet or mobile connection and will count towards any data usage thresholds that may apply.

https://www.xfinity.com/support/articles/live-tv-streaming#:~:text=When%20you're%20in%20your,Xfinity%20Internet%20monthly%20data%20usage.

Please confirm what is correct as your support team is contradicting your website and I don't want to get a bunch of surprise charges for streaming over a Roku.

I would like this in writing to make sure that I am not getting charged when I shouldn't be.