Interesting. I guess maybe some further testing is needed then. I'm not sure how that power bank was operating since it is USB A not USB C, so perhaps the USB C ones will fair better. It's still bizarre to me that a 5V / 1A is enough to up charge an iPhone 7+ while in use (which can deplete just as fast as the Switch under heavy load and doesn't have that much smaller a battery), but a 5V / 3A would not be enough for the Switch... weird. And all my iPads also can up charge while in use from battery packs as well, so it is strange the Switch isn't able to, despite having access to even higher charge rates from USB-C than the iPhone or iPad get out of USB-A.
It does look like going through the comments in that Ars article a few PD USB Type C chargers are mentioned, like this one from
RavPower, that's basically the same size as the earlier one I mentioned, just slightly more mAh, and supports much higher output: Type-C Output: DC 5V/3A,9V/2A,15V/2A,20V/1.5A; and
this one from Razer, which is smaller sized, only 12,800 mAh, but supports higher output as well: USB Type-C | 5V 3A / 9V 3A / 12V 3A / 15V 3A / 20V 2.25A.
Other than those I don't see any others, oh there was a Dell power bank mentioned as well, but then those three would be about it at the moment.