Never heard about lowering compression for an lpg burner. Why would you? Lowering compression for a turbo, that I have heard of.
Normally lower compression engines are to be run in countries where you cannot get good quality petrol, in the old days, 4 or 5 star. and I don't think this goes on much nowadays, but then i may be wrong.
Like unleaded petrol when it first came in, i think ignition timing has to be altered but that is dealt with by the computer that comes with the system. I hope!
Anyway here is a thread that shows it ain't obvious!
https://forums.lr4x4.com/topic/48291-lpg-ignition-advance/
and these seem to gainsay your mush about compression being lowered for LPG, in fact the opposite seems to be true.
https://www.google.com/search?q=Why....69i57j0l4.7009j0j15&sourceid=chrome&ie=UTF-8
All i know is mine runs fine!