The CC has supported DD+ from day one. There have been several threads about this. Allot of the problem is the source material doesn't really have a DD+ stream. Netflix has this happen allot. They have allot of content marked as 5.1 and only half of it actually works that way. TV shows are notorious for that.
It is also effected by how your devices power on. I have experience on my AVR where the CC only sends stereo. This was triggered by a condition where my AVR was doing pass-through and the TV only accepted stereo. Once I powered on the AVR the CC continued to send stereo, even though the content supported 5.1 with DD+. I had to completely disconnect my phone from the CC and restart Netflix to correct it.