I like linear piston generators. Have you seen them?
Discussion
That one looks like a Detroit Diesel 2 stroke, but more complicated. My main reaction is "what'd the camshaft ever do to you?"
I mean it's simple, it lasts a long time, it works. If you want it to do tricks, there's VVT.
Maybe that engine is designed for an application where space is at a premium so a crankshaft takes up too much space (?)