"Abolish the police" is pretty much right out of Kropotkin, and a lot of people aren't comfortable with that (perhaps rightly). "Abolish" as opposed to "disband" is a deliberate nod to "abolition", as in slavery abolition. See also: the meme about how modern policing is descended from slave patrols in the Antebellum South (based on my non-professional reading, this seems to be half-true, and it looks more like modern policing developed in 18th-century England).
ACAB... meh. Because of the power dynamics involved, I see nothing wrong with assuming that any police officer is hostile and a threat to your life and liberty. Police departments generally seem incapable of regulating themselves effectively and seem mostly immune to civilian oversight. Maybe there are exceptions in certain parts of the world.
I do agree that some people take "defund" further than others. I also think that a lot of people are "defund revisionists" to some extent, who are squeamish about really aggressively defunding in starve-the-beast fashion, much like how people are squeamish about "abolishing" the police. But I don't think it's a bad thing that any given crowd doesn't agree on what exactly it means. Politicians seem to be more or less uniformly interpreting it in the way I described it.
The other slogan doing the rounds at the same time - "all cops are bad" - suggests that there was a serious element who wanted to abolish the police on the basis that the entire police force was bad. That needs to be acknowledged if people are arguing about what the phrase means.