Author here. It does not need USB PD for power, it uses regular 5V USB and consumes less than 1A (usually less than 0.5A). The reason it supports USB PD is for the DisplayPort Alt Mode to allow power + video on a single cable. DisplayPort Alt Mode is part of the USB PD, to do DP over USB it has to support USB PD and communicate to the host through the PD that it's a monitor. Inkplate is a different class of device (has it's own processor, targeting lower frame rate, etc.) and we are not trying to compete with them.