The agreements each foreign entertainment company has with avex is not one-size-fits-all.
avex is a large company, so it is much easier to have them sign with avex and get distributed throughout Asia.
There is nothing wrong with that.
I'm going to say this:
If Utada signed with avex, there is not way she would be the same artist she is today. They would not allow her the same artistic freedom and musicianship that her current label does.