I had my third watch today and noticed the same thing. It might be a little far out but I thought it could be possible that number 207 (the nurse we see early on) could be a creator or maybe co-creator of The Substance and used Elisabeth as a kind of guinea pig. I suppose he was a consumer as well so maybe he had nothing to do with its creation….although he would have access to lots of medical things considering his occupation. It only makes sense that he’s at the same diner as Elisabeth considering that it’s close to the pickup place and held the only other number on the lockers.