I have had the opposite problem. I purchased a kit from a very reputable company's website. Didn't open and measure every piece right away tho. When I got around to making the quilt, about a year later, I found that the kit was short by a significant amount--so much infact, that I had to substitute one piece of fabric completely and recalculate sashing thru-out--I had less than an inch left of the sashing fabric!! I emailed the company and never heard a single word back. Will never ever buy from them again!!
When I'm buying fabric for a pattern, I usually buy a quarter yard extra in case of 'wrong-headed' cutting.