The study I read: Olive Oil Addition to Yeast as anAlternative to Wort Aeration
Olive oil was never meant to be used in the actual beer. It was an alternative to aerating. The purpose was to find an alternative to aeration, not to increase yeast activity. The thought is that on a high scale level, oxygenating the wort could cause off flavors (even though it is tried and true). Olive oil was used in yeast storage, not directly in the wort.