BadNewsRef wroteAnd he is going to say "WTF!!! Call the obvious, enforce the rules, and quit trying to be cute"
Again with the word "cute." Since when is using your brains "cute?"
To answer your question, though, it depends. If there's a chance of retaliation, of course, step right in and call the foul immediately. If A1 has a clear path to the basket, then a whistle would only benefit the defense, and I may pass on it entirely. Or, it be a delay. It's not the same call every time; it's an HTBT.
BNR, if your supervisor would stomp you a new mudhole for not whistling it right away, I'd certainly advise you do what you're told. ("When in Rome.") I have no clue how my association feels about this, because this is beyond a once-in-a-blue-moon thing. My only point is, without explicit instructions (for which I've yet to see citation), we're left up to our own ideas and influences.