My best guess is they don't need those exotic high temp alloys.
Most probably they run rich mixtures in the tji pre chambers which seems to be sized to contain and localise any detonation. Rich mixtures burn readily at the optimum temp and the ultra lean mixtures in the main chamber benefit from the high speed of violent ignition. The Mahle literature suggests that the mixture is ignited as soon as it is injected in the prechamber. It's almost spark assisted diesel. Any soot and co generated will be burned off in the main ignition event. It's only 3% of the injected fuel anyway.
I think this can be done as a retrofit in existing engines. Even an aircooled vw type 1 can work.