Strato development was driven by the need to meet emissions rules. Just like with everything else a corporation will not spend a penny on R&D unless they think they need to, and that is usually in response to an aggressive competitor or regulations. Like many industries chainsaws had consolidated into commodity products made by a couple of manufacturers that were fat and lazy. They each had their comfortable share and so they could cut development costs and rake in the profits as long as no one rocked the boat too much. Usually in that mode the main focus of whatever development money is spent is on reducing costs. That's a very common situation and doesn't lead to technology advances.
It takes something to disrupt the fat, dumb and happy party in order to get the development ball rolling. With the new regs smaller companies saw an opportunity (Zenoah) while others decided they would rather go out of business (McColluch).
Reducing emissions means improving efficiency, and that in turn is generally related to improving performance, just as it was in the automobile world with EFI, and now variable valve timing and direct cylinder injection. Remove the pressure of meeting tighter emissions targets and the manufacturers will reduce their development budgets and increase management bonuses.
The strato design is an elegant and effective solution, requiring only one additional moving part (the air valve) and directly addressing the scavenging loss problem. Strato allows different port timings which improve power output. One example is that the angle between exhaust and transfer opening can be reduced because this doesn't result in as much unburned fuel lost out the exhaust port. The GZ4000 is a far stronger saw than the G3800, much more than the 2cc would account for. I doubt the slightly reduced volume of mix passing through the case will be a problem from a lubrication point of view, and I'm not sure that the cooling is reduced overall as there is a greater volume of air moving through.
The other half of the emissions problem is the terrible mixture control of traditional carbs, and this is now being addressed with feedback carbs.
