Not so sure about that, muti-strike helps a bunch, at lower RPMs.
Stratified charge is also a means to insure more complete combustion. Getting complete combustion over the complete dynamic operating range of an engine, is hard. But what we are accustomed to, is what we think. We tune the best we can, but there is often more power to be found. To find, one must measure, few have all the tools, to measure all the aspects of combustion process.