Remove existing DataRows when provisioning list Data Rows using Office Dev PnP Provisioning

Isn't the general idea that what you export is what you import. So that the .pnp file becomes a tmeplates that is saved from the site.

When you use Datarows you will have manually added that to the xml file. (I've done the same in past projects)

Therefore deleting the items with additional PowerShell isn't a bad idea.

I'm comparing this a bit to the issue that I resolved where only the welcome page is exported. To recreate all the other pages in my site I created an additional xml called pages.xml. In this file I specify the page details and the web parts on it.

Maybe for your datarow issue in lists you could do the same. Specify the lists where you want to clear the data from (assuming that you don't want to do this for every list) and then get some PowerShell to clear the lists from their items if needed.

If've not tested this but if you are just after not duplicating the items you could include a unique field in your datarows (e.g. ID) so that the uniqueness will make the recreation of the items fail.