Sort of. C rate discharge is just another (confusing) way of state CDR. You might as well just say the CDR in amps. C rate is really just to give a comparison on battery chemistries to illustrate how performant different chemistries can deliver power at a normalized value (to illustrate how the battery chemistry could in theory scale up)

For example, 1C is rated continuous discharge amps, which means a 1C rated battery will provide 1 * Ah. So if a 20,000 mAh battery is rated for 20,000 mAh @ 1C, it will (in theory) discharge 20,000 mAh at 20A in one hour.

> You can of course estimate the battery capacity in watt hours, but it’s not how the battery is classified (eg in a data sheet)

You're right but this is irrelevant because real life usage highly varies. Data sheets are just guides.