Millions of them screaming (and I mean millions, and I mean screaming) around China no problem. They are available all over the world except America.Yes, that's probably a big factor. Also, the variable valve timing on the K Series doesn't offer much in an airplane aside from additional complexity. But, I don't know much about these engines, maybe they are super.
I don't fall for the "complexity" line, engines in cars today are just fantastically reliable, far, far more so than the "simple" engines of past decades. No manufacturer has VVT issues in terms of actual mechanical failure.
200,000 ~ 300,000 miles is nothing for an engine these days.
But still, interesting to see the mindsets, clearly myth and lore are absolutely deciding factors, and the reason I was looking at carburetor suppliers this morning ...