Xfinity Stream on Samsung TV

First, this question has been asked before and the resolution does not apply to me, so please carefully read the issue.  I have a Samsung TV with the Xfinity Stream App.  Currently, my non-HD channels do not show on the full-screen, even though the app and menu do.  Please don't respond and tell me that the solution is to sign up for HD technology fee, this is an Samsung xfinity app issue, I'm not concerned about HD versus SD. These channels are not showing up as 4:3 shows, I'm getting a a broadcast that's roughly a 16:9, but letterboxed/black border all around.  I have another non-Samsung TV with a built-in Roku and Xfinity app, and this is not an issue. On that TV, all my non-HD channels  fill the screen.  On that TV, for older shows that are 4:3, they at least fill up the top and bottom.  On the Samsung, even an older 4:3 show has letterbox all around.   Again, this isn't about HD versus not HD, or widescreen versus 4:3 ratio.  This is an app issue where it's not fitting the screen.  My 65" TV looks like it's a 50" tv because of the letterbox all-around.

Again, please don't tell me that I need HD subscription to solve this issue, it's not an issue on any other device or non-Samsung TV with Xfinity app. If this was an HD subscription issue or SD channel issue, for shows broadcast in 4:3 ratio, I'd have a letterbox only on the sides for those shows.  I'm getting letterbox all-around regardless of show type.