You cannot even run these misnamed Atkinson cycles under many combinations of load and rpm.
They are in the main, completely incapable in terms of high load higher rpm operation.
- and for a different but partially similar load of fail down low - but with load.
They knock and detonate like no tomorrow - w/o assistance ala Mazda - yes it is true this thermodynamic abomination ( @ low rpm with load ) can be helped with the right kind of boost - and fuel trim etc.
Or a big enough battery or other member assist.
Then, you also have to subtract off where you 'could' run it, but other choices - not the least of which is a dreary and drab Otto cycle would 'out perform' it - including massively.
It does have a role to play but it is extremely limited - like a niche unless you combine it meaning utilize it as but one tool in the box ie with multi modes of operation.
Oh look, we're back to GM ......
Which truth be told, is the most likely case with what Honda is bringing ie part time 'atkinson'.
And within that, for certain specific cruise conditions and light acceleration - at best.