To me, "root DNS servers" means 198.41.0.4, etc.

The names and IP addresses in the responses from those servers, i.e., the DNS data in the root.zone file, were not "wrong"

The story being told is that some, not all, of the .de nameservers, i.e., 194.0.0.53, etc. were serving incomplete zone files

DNS worked fine. The responses that the root DNS servers were sending were wrong.

It's the cryptographic version of that one time the same TLD told the world domains starting with certain letters didn't exist: https://www.theregister.com/2010/05/12/germany_top_level_dom...