I have no idea why they made the changes. I follow two people on you tube that use the ECO-W. Both use 2 150w panels, one in series, the other in parallel. The person using them in parallel had over heating issue but not the other. He has had his Eco-W pass 20a at times.
I can say that I had already decided that 270w would have to be my limit due to the boost I get at altitude. I've seen over 17a off of the 245w panels and that was a clear sky too, no cloud effect. Another 30w should push it to 19a or so with just a bit of leeway.
Now here is a question. Is 275w a limit for the rating of the panel or actual production? The 245w panels are doing good to produce 220w each, the 230 212w. When I talked to Marc at Rogue he was fine with putting more than you would think would be ok because he didn't expect to see actual watts above the controllers limits. I would expect it would just shed excess amps if it did. MorningStar even promotes over paneling.
I'll add that question when they respond.