That is because Zoche and other projects like it exist to absorb development money and nothing else.
It would be fun for a day or a week, until the realities start sinking in. Those realities are what have kept new engines from appearing regularly, and not appearing affordably at all.
How many here remember the Zoche diesels? From Wiki:
The testing and gestation period of the Zoche engines has already lasted over 25 years; and whether or when production may eventually start is unknown. However, in 2019, Georg Zoche posted this message online: "Don't worry and remain patient; we are working on it".
Zoche aero-diesel - Wikipedia
Nobody is holding their breath anymore. Most don't think it will ever be available.