There are people who actually like the X3D + non-X3D setup. Here's Bryan Heemskerk giving a glowing endorsement of the 7950X3D while talking with MLID.I don't get it. Is there really a market for these chips? Literally every AAA game can be perfectly played with a regular Ryzen 9 9950, so why would a professional content creator sacrifice quite some rendering performance in order to get a few more meaningless fps? AMD should rather push more 9800X3D chips for the gaming crowd and more 9950 CPUs for serious workstation tasks instead of wasting time and precious resources for a "Frankenstein" 9950X3D that presumably nobody needs.
I think that type of buyer is rare, and many were disappointed that both CCDs don't come with V-Cache (whether they actually need it or not). There are some professional workloads that benefit from extra cache (that's why Epyc X3D exists after all), lower power used in some scenarios, and no scheduling problems if both CCDs were to have X3D.
As an example, almost everything on this page of Phoronix's 7950X3D review benefited from X3D:
https://www.phoronix.com/review/amd-ryzen9-7950x3d-linux/9