Correct. No Curves yet in Photoshop for iPad.
Photoshop for iPad is missing lots of core features that we rely on in the full desktop version. Suggest you familiarize yourself with the available tools in Photoshop for iPad before you buy your iPad Pro to avoid disappointment if tools you need are not there yet.
Many people assumed the first release would include all the main features. That did not happen and was poorly communicated by Adobe.
Hopefully they've now learned how to set expectations: under-promise and over-deliver.
More features coming throughout 2020 according to Adobe.
Curves has been added with the latest update to the application
Curves are on there now and they work amazingly