Ah, so that's why I doubt my ability to properly taste (and maybe smell) my flavors. Interesting point and thank you for that. I just got a reply from a friend on another forum who said that she received a mistakenly labeled flavor from a vendor whom I shall not mention out of courtesy. Now I know that that is a possibility, too.
However, the point of single flavor testing is an important one that I feel I should be more disciplined with.