BeagleBone Black automatic power off sense issue with device trees

I’ve got a BBB that I’m using with a battery attached to allow cleanly shutting it down. I’m running it currently on the 3/15/15 release of Debian.
If I run it with the default device tree (am335x_boneblack.dtb) then when 5v is removed it shuts down properly. If I use a dtb that doesn’t have hdmi enabled, (i’m using an LCD cape), it doesn’t see the removal of 5v and continues to run.
I did some experimenting and found that if I use a dtb that has the hdmi in it, but not the hdmi audio, it would not shut down. It appears that the hdmi audio is involved with shutting down the BBB, or there is some unintended interaction.

Any one out there that understands this better than I do that can help me figure out what is going on?