I don't really understand how that's a paradox. It's a natural result of the mathematical properties of the average, if outliers are a problem, we use median.

I wish it were not the case but "paradox" can be used to describe apparently contradictory behaviour even when its not actually contradictory.

What other definition of paradox is there?

Yeah, a literal contradiction. The purest example would be Russel's paradox: https://upload.wikimedia.org/math/b/e/0/be0bd5b59ed09618db93...

I like this variation:

"Both of these sentences are false. The sky is not blue."

It could be a literal contradiction, for example for someone religious, it may be paradoxical that evil exists given the existence of a benevolent all-powerful being, since that being either is unable to stop it or is choosing not to (which seems either not so all-powerful, or not so benevolent). Rather than change any of the beliefs that imply this paradox, believers can accept the beliefs and instead address the paradox through some other means, if at all.

I find that most of the time the word paradox is used when a description of a situation is done badly.