Sadly, it's been my experience in 3 years of LCing that labels are a 80-90% proposition at best.
One of my few comforts is the actual lab-testing (burn! burn! LOL!) that went on a year or 2 back, through the good offices of the venerable LowCarb Retreat (Lee Rodgers' site, he's pretty well one of the 'grand old men' of LC). See:
http://www.lowcarb.org/tortillas.html
The first lab test (WASAs, LaTortilla(s) and BranACrisp) came up with somewhat disappointing but unsurprising label inaccuracies and the label always erred on the side of high carbs. Of course labelling law in the States, the biggest market, had been focussed on accurate fat and protein counts; there the FDA would land like a ton o' bricks if there was complaint. Anyway, to make a long story shorter, the 2nd test round declared the 3g effective carb count to be accurate (there were finally complaints and they changed the formulation by adding roasted soy flour and fixing the label).
Of note, there are a number of foods manufacturers that calculate fiber as calories, especially soluble fiber, because of that orientation of the FDA-controlled labelling laws. See the Expert Foods labels, for example. Those products are essentially all soluble fiber carbs (vegetable gums)... there's also a very well articulated and researched discussion of US labelling laws and why things are as they are, which is of course SKEWED from a LowCarber's point of view. See
http://www.ExpertFoods.com if only for the info on labelling, it's amazing.
All else notwithstanding though, many have a sensitivity to grains or soy or what have you, so YMMV [ Your Measurements May Vary ] and it's probably best to take a cautious approach and watch one's reactions, as Rachel does. It's responsible and practical! It's safest to Do The Match and to have fewer carbs than more. They can be sneaky as we all know!
Well, I'll get off my soapbox now [ grin! ]