Hmm...I guess you did not read the article, which stated it does not need to be contact cheilitis since you can have reactions elsewhere in your body. Believe me, if you eat something you are allergic to, it is common to have a reaction on lips. For example, many people who are allergic to wehat have reaction on lips from ingesting it.
By the way, many of us did not develop EC from trauma. You either have different cause of EC or link it to trauma when it may just be a coincidence. I am sure many people who bite their lips do not develop EC.