It's pretty standard as nationwide protocol; or at least it's what's in textbooks and taught in police academy.
How exactly do folks who want it to be changed, think one would go about getting truth out of a subject in a he-said, she-said situation?
If the officer doesn't identify with Brian, and treats him hostilely as part of the discussion; that makes it worse and has the possibility to make Brian worse.
First people were upset that "Gabby didn't get a chance to talk to a woman alone", then we in fact did find that she was separated and questioned by a female member of the park police; and then people suggest Gabby would have been too intimidated by HER uniform in order to speak honestly.
Interrogators must enter into the language of the interrogatee (? not a word, I probably know). It's standard trust-building behavior, which both sides of the equation are supposed to get (because aggressing towards people who are discovered to have weapons could further endanger both cop AND Gabby if Brian had felt threatened); and which it seems both the male and female half of our arguing couple both in fact got.
This makes tons of sense, and I wonder how people would suggest legislating that we fix this? Clearly the shelter doesn't want the violent person under their roof for CYA, because if the violent person attacks another resident or worker in the shelter, I'm sure there's a lawsuit there.