A device doesn’t charge anything doesn’t mean it can’t take advantage of the PD protocol, like HomePod mini requires a certain volt-amp combination over PD or it doesn’t boot. Ask me how I know.
Also my goal isn’t to reduce the number of chargers I bring, but rather every one of my travel devices can be packed in to small hard cases and the stock adapter obviously won’t fit. If someone have a charger current meter maybe he can tell if Beryl does negotiate a wattage, or not and the charger just defaults to 5V.
Anyways thanks for all the info, now I know how to pack my new router (when I get it)…