
Maybe more realistically, you could have a player who surrenders once every 10 games on average, so sometimes they would get booted from Ambassador class, but then they would usually come back after three finished games as a Diplomat. So they would spend some fraction of their time as an Ambassador. (In fact, if you do the math it such a player would be Ambassador about 60% of the time, ignoring the possibility they picked up surrendered powers.)
So yes, there's a chance you'll run into Ambassadors with 10% surrender rates, but I suspect that there aren't so many people like that: it seems like if you don't care about surrenders, you would have a higher rate, and if you do care about surrenders, it would be lower.