Previous experience. With DC "the wost" it's a pretty sure bet.
If Mary is naming her kid after her ex she hasn't really moved on.
It makes no sense to have your son named after your spouse's ex, unless it's your brother or father but that would be a different kind of mess.
The whole thing ended being underwhelming; the cool villian is out, bludhaven and it's things are staying. Future is looking very lackluster.