I just noticed today that in a render layer node where I have every check box turned on, I have four undocumented render layers that don't appear to have any check boxes, but are being output anyway:
I'm pretty sure I understand what the words mean, but when I look at the actual images they are producing, I can't understand how to make any use of them, as the first three appear to be using a single channel, and the fourth is pure black in all channels. I am using version 4.4.49.
This is a bug in v4.4. These four files are accidental byproducts of the renderer. The renderer uses subpixel versions of these elements internally. It doesn't finalize them for output because they weren't requested in the UI, but they are output anyway, and this is the bug.
Thanks for the clarification! I will make a little clean up script to delete these from disk after a render sequence is completed until the bug is fixed.