It was significant when the full amount of food was given. when they considered everyone (including those who didn't give the full amount of food for the protocol) it then lost significance. This is from the NEJM paper:
"In the per-protocol analysis, the prevalence of any food allergy was significantly lower in the early-introduction group than in the standard-introduction group (2.4% vs. 7.3%, P=0.01), as was the prevalence of peanut allergy (0% vs. 2.5%, P=0.003) and egg allergy (1.4% vs. 5.5%, P=0.009); there were no significant effects with respect to milk, sesame, fish, or wheat."
Article with full details of relative risk and confidence intervals here:
www.nejm.org/doi/full/10.1056/NEJMoa1514210#t=articleResults
I'm not for a second advocating that children should be weaned at 3 months on the back of this study, and agree that other signs of readiness are more important. The study authors themselves state that giving the full protocol was difficult.
I have however come across a few HV who are convinced that any food before 6 months will do catastrophic damage (no real evidence for this), and also some who have linked early weaning to greater risk of allergies (it looks as though the opposite might be true). This seems to stem from a slavish adherence to the guidelines, and I wonder if a bit more flexibility might be more appropriate as evidence accumulates that earlier weaning can beneficial in some cases.