Correct. The other commenter is giving bad advice.
Both power delivery and bandwidth are backwards compatible, but they are independent specifications on USB-C cables. You can even get PD capable USB-C cables that don’t transmit data at all.
Also, that’s not true for Thunderbolt cables. Each of the 5 versions have specific data and power delivery minimum and maximum specifications.
You can even get PD capable USB-C cables that don’t transmit data at all.
I don’t think this is right. The PD standard requires the negotiation of which side is the source and which is the sink, and the voltage/amperage, over those data links. So it has to at least support the bare minimum data transmission in order for PD to work.
Technically, yes, data must transmit to negotiate, but it doesn’t require high throughput. So you’ll get USB 2.0 transfer speeds (480 Mb/s) with most “charging only” USB-C cables. That’s only really useful for a keyboard or mouse these days.
