From the chat operator: "Yes this issue is actually a know issue, HBO go app does not show option for Comcast subscriber, We are working hand in hand with HBO GO developer to update their app and have a Comcast option as a provider."
"We are not really sure when would the update happen since we are still negotiating with HBO GO app developer."
ME: "And this is for Android TV devices?"
"All capable devices that can access HBO GO app , Like smartphone SmartTV etc."
It's not an accident that Comcast doesn't allow you to use your Comcast login info with HBO Go. They do it on purpose just like they do for the majority of other network apps you might want to use their login for.
They make a lot of money by renting additional boxes to people. Allowing their customers to login with their account info on Android TV apps is in competition with that rental revenue. It's why only an altered version of the Xfinity Stream app will work when sideloaded onto The Shield or Mi Box. They are actively trying to prevent AndroidTV users from using the Xfinity Stream app with their valid account info.
Don't read into that too much. They told me it's coming in the 'near future' over two years ago.
Because Comcast Cares.
I can almost guarantee the person you were talking to has no clue what Android TV is.