I havent looked into the sizing myself, but if its true that the cx-5's 19" tire size selection is limited to only those toyos, it is most certainly an issue. a big issue.
Non-issue, anybody can go to different sized tire like a 235/50.
But the 225/55/19 is thoroughly engineered into the car and even though they were rare in retail channel on day 1 of product launch, 8 months have since elapsed. Issue is just the usual internet hype, an issue in some peoples minds, a small issue.