I don’t fault the cops in this one. They’re not psychic. An assault allegation was made and they arrested the accused.
But they also followed up and found what really happened and are now landing on the actual perps.
Perhaps I’m not up on NY laws, but I cannot imagine it would be much different elsewhere. In Texas, unless there are corroborating serious injuries, or a police officer witnesses the assault or has an issued arrest warrant, mere accusations are only the cause for charges to be filed. Otherwise, abuse of the justice system would be rampant to “get even” with someone on unsubstantiated charges.
As a former cop, I received plenty of assault accusations in the heat of an argument, but later, the complaining party almost never wanted to pursue charges. Turns out that they were usually false reports, and the complainant knew that their neck was on the block if they went forward with the charges, much less insisting on arrest. (The only exception is domestic violence where the parties are at higher risk being forced to live in close proximity.)
This is typical sodomite behavior. Apart from their other vices, they tend to be inveterate liars, as Kirk and Madsen attest.