If anything, I would want them to push the start of the season back to November. Get away from the MLB post-season.
As far as being unacceptable? Not sure it would be "unacceptable". It is simply business. In September, you have the start of the NFL season, you have MLB pennant races. Secondly, most North Americans really do not care about the World Championships, so they are not going to change their calendar to accommodate a tourney for which their customer base has little interest.
Could also be temperature related. I know in April, May, June, arenas have a harder time with the ice as the warmer air gets into the arena. September is still hot for the most part through most of the US, not sure about Canada. I can't remember hearing this mentioned, just speculation on my part.