These devices run on 5V supply, which is easily supplied using any USB version.
The higher voltage 12-24V is only required when the device also has “passive” PoE-out, indeed to reduce current towards the next device.
“real” PoE usually uses 48V.
I’ll stop right after title of document:
Universal Serial Bus
Type-C Cable and Connector
Specification
The emphasis is mine.
The thing is similar to saying that UTP (or RJ45) is ethernet. But we all know that UTP is cable specification, RJ45 is connector specification (and both can carry wide variety of protocols) while ethernet is protocol (which can use physical infrastructure other than UTP/RJ45).
The only unfortunate thing about “USB-C connector type” is using “USB” in its name … because that largely hides the fact that not only USB protocol is carried over these connectors.
When it comes to voltages: USB PD standard version 1.0 only defines a few discrete voltage values (5V, 9V, 15V and 20V IIRC); newer standard revisions are adding higher voltages. Only more recent USB PD PPS standard allows for fine-grained voltage negotiation between PSE and powered device. So when thinking about using USB PD to power anything but wAP lite devices, one has to consider allowed input voltage range for certain devices (some only accept 18V+) and USB PD power source (which has to support 20V, not all of “smart chargers” support that).
Keep in mind that USB PD doesn’t require USB-C connectors … only high current modes require USB-C connector due to better(?) connector design.
Glad you concur rj45 isn’t ethernet as much as the connector isn’t just usb-c. 
I’ve trouble deciding whether you’re being sarcastic (about USB-C being connector standard VS about-everything standard) in this thread or not. Or better: do we actually disagree or not? Would you mind helping me decide?