Pioneer’s 2012 code documents don’t show such an input existing, so let’s assume they made an error. Meanwhile, we’ll add INPUT UP/INPUT DOWN and INPUT HDMI to the next drop which should at least be able to force it. Another way to force it should be to unassign the HDMI numbered port from the GAME port. When an HDMI input is unassigned on Pioneer, it re-allows you to access it directly. So for instance we have all 7 HDMI inputs for Pioneer models, but numbered ports are rejected if you assign a port to a name. For instance, if you assign HDMI 5 to BLU RAY, the INPUT HDMI 5 command wont work anymore and Pioneer will require you to send INPUT BLU RAY. So you can probably also force it by unassigning GAME from the port and then use the correct HDMI input name instead.
Finally, we can also extract the input from the unit using Collect Diagnostics. When 1.5 is live, turn that on, open any Activity with your receiver as Volume Control, and then manually set the input to the desired input using anything such as the dial on the front. Let it run for a few seconds until Roomie updates the display and then tap Send Diagnostics and let us know.