I agree with the team-size aspect, but the age argument won't always hold.

Junior folks bring their own energy, flexibility, hunger for learning and the resilience to unclear future. As folks get more mature, growing egos, stability expectations, tendency to settle down can get in the way.

Overall, this boils down to the fact that teams and people are not just head counts and there's a factor of chemistry need to be considered depending on the culture, founders, geography and the business itself.