As I understand the issue, the Yamaha EF2000iS produces a pure sine wave that is great for computers and other critical devices. However, when an air conditioner starts, the very heavy load will cause a generator's output sine wave to distort, which can harm the Progressive Industries' EMS units. The bigger the surge demand from the A/C, the greater the problem.
Rather than checking with the generator manufacturer, it would be better to get an answer from Progressive Industries. They say they can't test every generator on the market so they may not have an answer. Additionally, their literature, under "Warnings," says, "Never plug EMS into an inverter."
I am aware that some people use their inverter generators with their EMS and have no issues. Again, call Progressive Industries for their take.
2015 Wildcat 282 RKX
2011 F350 Lariat, 6.7 L. Diesel, 8 ft., SRW, Reese R20