Hmmmmmm.............interesting question. The honest answer is I have no idea and need to get in touch with the builder. I'll be back to you in a few days.

Finally heard back from the builder. He used stone up to the opening for the TV and then used a tile backer board behind the unit. He did waterproof this opening very carefully even though it it well under the roof of this porch.

Thanks for the response. I appreciate it. I wonder if he painted the backer board so that you couldn't tell it was backer board. It looks like you can see behind the tv.

Now that I look at this closely, I think you're right. It looks like the same color as the wall shingles.