My guess to why preignition would exist is due to varation in the temp of the combustion chamber thus if the kero air mix on the compression stroke sees over 410F its going to ignite before TDC. And varying CC temps will cause the airfuel mix to sparattical combust varying ignition timing. So if you put a good load on the engine it would raise the CC temp and cause preignition.
Now i have no idea why preignition is not a issue with compression ignition models usings carbs and compressing the fuel air mix. But thats where the contra pistons comes in it controls pre igniton by varying compression. I guess??
I dont have a model diesel yet.

Direct injection is best as we all know but complicated for models[:@]