Yes and no.
The hardware obviously supports it, but the android SDK doesn't provide a way for userspace software to implement new devices, so you are stuck with the devices already there. And you really want this to work on any phone that the survivors find, without any pre-apocalypse prep work, so assume rooting is out.
Testing on my two Samsung phones, while you can connect them, and charge one from the other, I couldn't manage to transfer files from one to the other. Even though they have this and use this functionality in a built-in to migrate from one phone to anther during upgrades. Maybe there is a way to get usb networking working?
TBH, I think you are better off just relying on adhoc wifi networks created by the phone sharing. Slower, but it doesn't require a usb-c cable (and these phones might get all sorts of hardware hacks applied to charge them, some of which might interfere with usb-c)
> We need solar powered wifi with suites of bootstrapping APKs.
Once again, that's pre-apocalypse prep work of hardware, which we want to avoid. And can be solved easy enough post-apocalypse. Just find a phone. Hook it up to a solar charger, and make it host an ad-hoc wifi network and run the syncing APK.
My hope is that a few people are paranoid enough to stash the APKs and some useful databases on either flash drives or their phones. (alternatively, make at least some of the databases useful enough that some percentage of the population is incentivized to naturally carry them around on their phones. They might not ever use the phone-to-phone syncing, except in weird situations when multiple people are out of range of the internet). And then once the apocalypse happens, hopefully enough devices capable of charging phones will stick around until the dataset spreads, and people use the infomation for making/maintaining power sources.
Then we are reliant on the massive install base of android phones, scavenging and the long-tail of the bell-curve keeping enough of those phones functional enough, with the data hopping from phone-to-phone until society reaches the level of technology where they can build new storage devices.