@Snapsy, I believe it! Years ago, when the Nestle's vanilla creamer first came out(i am a huge coffee drinker) I accidentally left it out on the counter and went on vacation for week. When we got home I was really upset because the first thing I wanted was coffee with my delicious creamer. Lol. My husband tried it and was amazed it was still edible. Yuck! But we didn't know! We know now. US is huge in gmo's (fake food).
I read relatively recently - it might even have been on here - that if you put a chunk of butter outside, and a chunk of margarine, the butter would very quickly be eaten by animals whereas the marge would stay untouched, due to not being actual food....!
Perhaps an urban myth, but doesn't sound that unlikely!