Fair enough. I was relying on e.g. Librem 5 USA - Read Before Ordering - #129 by dos but it does depend on exactly what “non-PD sources” means or for that matter what protocols the USB-A port at the supply end is capable of.
All the more reason to need diagnostic tools for when the power protocol doesn’t work.
I come back to: Or maybe USB-C chargers will come with [a USB power meter] built in.