When you cut a person out, you are removing their power over you. They apologize to get power over your emotional state back.
The narcissist doesn't feel empathy for you. The apology is meant as a transaction, not an expression of guilt or an admission of wrong doing.
That's why when you test the apology ("you'll stop this behavior that results in me feeling bad") the test fails.
The reply from the daughter was an attempt to set a clear boundary while also showing appreciation and support for his change. I think setting boundaries like this is a perfectly healthy thing to do, including/especially towards family members.
I'm completely fine for my comment to prompt people's own takes, as you gave in your second paragraph, in response to my observation.
People are entitled to set and enforce boundaries. Given that dad is abuser, this one is very healthy one, because it allows the daughter to keep her freedom.