Wattage is what you get when you multiply amps and volts. You just said the equivalent of "It's not about the ice cream, but about the ice and the cream".
Also, it arguably does have everything to do with volts - if you put the too much voltage into a device, most likely you're going to damage the device, its surroundings, or yourself (i.e. in a house fire).
USB-PD on USB-C negotiates the highest voltage your device and charger will support.
You can buy a 30W USB-PD charger that supports a smaller subset of voltages than a 20W USB-PD one, and in practice will deliver less power to your device because the voltages both like don't line up well.
What actually is supported by each tends not to be specified/disclosed-- or if it is, it takes a lot of digging to figure it out.
Oh? Everyone else seems to think the mechanisms are sufficient for safety.
> This wasn't my point, despite me addressing negotiation in another comment.
I still don't understand your point, unless it's a failed effort at pedantry.
Also the original comment was unclear; they've edited to clarify. But of course, I'm the bad guy on HN for not being able to read minds.
E: I realize my GP comment was also unclear. I should have said "excessive" voltage, not improper I suppose. "Improper" in my head meant outside the rated voltage for either end/the cable. I'm not the one being a pedant here.
Which is exactly what GP was saying in the very part that you quoted:
> chargers and cables are advertised with the wattage they support, but it's really the voltage and current that matters.
and what you agreed with in that very same comment:
> Also, it arguably does have everything to do with volts
The important part with regards to power delivery isn't simply wattage. If a hypothetical charger can put out 96W at 1V@96A, it's never going to deliver even close to that amount of power to a device that expects 96W at 20.5V@4.7A.
OP is complaining that that leaves the true wattage of a given device/charger pair unknowable from the charger's packaging alone without further information as to what voltages and at what currents it can supply on request from the device. It's certainly a valid frustration.
It’s the end device that cares about voltage and amperage both as the voltage steppers inside have to be ready to handle providing the right voltage to the chips and the amperage has to be right to handle the load.