His statement could probably be better refined as "largely keep their opinions to themselves and do their jobs."
IME, older workers were raised not to discuss politics or religion at work.
Younger opinions are easier to influence. Older opinions are pretty ingrained which makes them annoying to deal with when they come up.
Translating: "People with little experience have ill-formed opinions and thus when you point out the holes in their arguments they cave, whereas experienced people have well-formed opinions which makes it difficult for you when you have weak arguments by which you try to change their opinion."
I agree with you but it’s still possible to make a perfectly well formed argument and still not be correct or the best choice for the situation.
Old people cost too much and speak the truth. Two demerits.
I think that depends on the personality, not age or maturity level.