Just because a child outgrows a food allergy does not mean that that child was never allergic to it, which seems to me on a quick reading to be what that article is implying.
I used to react, get a rash right There, to the snaps on my jeans. In the last couple of years when I've gotten new(to me) jeans and have not covered the button back as I used to, I have not reacted. Does this mean my previous quite definite reactions were a figment of my imagination? Or does it mean something in my body has changed and I no longer have that particular allergy?
Time was I could wear latex gloves while doing my EMS volunteering. To do so now could concievably kill me. Does this mean I can't be allergic now?
Our chemistry changes over time. That doesn't make the tests inaccurate. It just means that one test is not good for a lifetime, and that as things change one adjusts.