I feel like detachment can come off as maturity sometimes like when you're just not reacting to everything. But real maturity, at least to me, is being able to stay emotionally present even when things get messy. There’s a fine line between being grounded and being shut off.

It depends on the situation. Sometimes you can mature and it can cause you to detach. And then there are other times where you may be emotionally empty.

Both.
I know when to let things go and to mind my own business but I am more emotionally absent honestly.

It isn't about maturity to me.
It's more like the shutting down of emotions from a conscious choice or a result of past experiences or mental health conditions.

Is emotional detachment another word for not putting up with needy people’s desperate desire for validation?

Not certainy with the first...........

alongaloof

Not necessarily either. One can be attached and yet nature. One can be detached and immature.

The latter.

Depends on the reasons/cause

It can be either, depending on the situation.

It can be both depending on the situation

It can be both, neither or either, depending on everything

Context is key here.

Emotionally absent.