Just a guess, but perhaps the difference is that NY state has every reason to believe Jacob was murdered in her apartment. They refer to it as a crime scene.
Whereas, California police know M did NOT disappear from AB's home, and probably not even from California.
IMO, in order to detain someone, police need to convince a judge they have some credible evidence about the crime, and answering who, what, where and when...as best they can. Not just pure speculation, but actual evidence.
I imagine there's a lot of quiet searching around where M was last seen.
JMO
