Thomas Borchert wrote:

Diamond has
decided to offer Lycoming engines as an alternate for the Twin Star (which
must really please Textron)

Diamond has been bitten before when introducing a new engine to the US
market, the Rotax. So they're careful.

It's not only this.

First, as you've mentioned, the Thielert engine has not very much power.
So there is still a demand for the stronger Lycoming engine.

Second, Diamond is well aware that the first buyers of the Thielert
engine are beta testers. They have never made a secret out of this. So
they decided to sell the Diesel version only near their factory until
they have collected enough experience. Makes a lot of sense to me.

Stefan