Originally posted by MMVIII I tend to disagree. But I see a problem with my planned argumentation: backwards compatibility is also for USB-C given, you might always use a Standard USB A plug on the charger side. But I have to confess that I don't know if this then again requires internal electronics to reach the 8 V... my assumption is, that this is part of the specifications, though no additional electronics in the camera would be needed. It would just charge slower (regular) while with PD you could benefit from shorter cycles, as modern smartphones and other devices offer. But I'm now in guessing-territory...
Yes, a true USB C PD charger will deliver whatever voltage the device asks for in the range of 5 to 20 V. It's a viable option for charging 8.4 V LiIon batteries in cameras with a minimum of extra stuff inside the camera. But if you look at most off-the-shelf USB chargers, USB ports on computers, USB ports in cars, hotels, powerbricks, etc., they are the older spec of 5V. Those are fine for charging the single cell 3.7 V batteries in phones and compact cameras -- dropping 5 V to 3.7 V is electronically easy. But boosting 5 V from a standard USB port to 7 to 8.4 V for charging a 2-cell battery takes more electronics.
In essence, USB C PD chargers are backward compatible older USB devices but older USB chargers are not forward compatible if the device really needs something other than 5V.