A potential customer told me 'I don't need a contract, my word is my bond' when I sent over the paperwork. Is this a major red flag?

My game group in Denver tried a 10-hour Twilight Imperium session with a total newbie.

We invited my friend's partner who had only played Catan before, expecting to spend the whole day teaching. They picked up the rules fast and ended up winning by a solid 3 victory points, which completely flipped our usual power rankings. It showed me that assuming complex games are only for veterans can really backfire. Has anyone else had a beginner totally dominate a heavy game night?