This emissions thing was a big fad " Diesels are the worste pollutors, It was Honda that wanted 2strokes fazed out of GP racing.
the practically own the F.I.M. and low and behold , the"ve got rid, of 250cc Gp &125cc Gp races,,,, replaced by Moto 2 = 600cc [ Honda engined bikes] I bet Aprilla are sick , as they had the dominant 125cc 2T, Gp bike,,
If evolution had carried on, the 2T engine would still be the fastest & most powerfull engine ,