X1 boxes work just fine in surround audio. There are a few idiosyncrasies but X1 boxes work fine. There has been some recent issues with dropouts but Comcast is very aware of the issues.
When people complain about X1 and surround audio it is because of a lack of understanding or incorrect connections.
There is a thread pinned to the top of this forum about X1 audio. I suggest you read the last 5 pages of that thread. It should answer your questions.
There is no reason for Comcast to provide credits. X1 boxes work fine with surround audio.