B2N2
I don't think that much evidence of the burn has actually happened on LOP, to be honest it is only a cruise thing and that type of video tech is new compared to the motors we are talking about.
And nothing really new in this piston market, so why spend the coin?
From my old appy days I do recall a benefit from the burning exhaust gas exiting the exhaust value also creating a vacuum - that sucks in extra inlet fuel/air mixture.
It is on this old memory that I think even LOP has some unburnt mixture as the exhaust opens.
Not saying any of this post is fact just what I recall being told and the old motor stuff and actual testing.