This is the exact reason I don't trust any of these labs, as the results showcased by members like Shadowra aswell as my own testing that I sometimes do in my free timealmost always contradict these so called "independent' labs. A example being Kaspersky that consistently score 100% in terms of malware detection from testing conducted here, which I have also personally seen when testing it myself (I don't use it and i'm no fanboy, but it is a top notch product which we all know from testing.), and yet a couple of these labs show results as low as 97%. Yes, no product is perfect and can actually provide 100% protection, but inconsistencies this large make me very suspicious as to how they actually test products, or even if they intentionally scew the results.
Another example is TotalAV, one of those grayware products that use the Avira engine. Sometimes it gets the lowest score out of all tested products, and sometimes it get's a perfect result, outscoring even top products like Kaspersky.