It's unlikely (but not impossible) that a 24 year old developer has had much of the experience needed to be classed as properly senior.

Seniority is not about how smart you are. And most programmers of any age are neither prodigies nor geniuses.

Do not accuse people without evidence! I'm all against age discrimination.

..and when you see a company where the age cluster around a very small area you can tell age discrimination is happening. Which might very well be the case of the parent post.

It's even more complex as you cant even say dev X > dev Y for all tasks. So the age thing is even more silly. After so many years you start forgetting the stuff you did (in detail) in the first years anyway.

You're bringing up the exceptions that prove the rule as if they disprove it.