Correct a "rules" error?

[BayStateRef]

Fellow ref told me about this.

One-point game in final seconds. B has a throw-in on Team A endline. Administering official calls a throw-in violation. Team B coach asks what the violation was. Official says, "Thrower had his foot on the line."

Coach calls time out. During the time out, officials get together and calling official repeats what he told the coach.

You are the partner. You know the rule says the foot must cross the line and be on the court for it to be a violation. Merely touching the line is not a violation.

What do you do? Tell your partner what the rule says and allow him to change his call to inadvertant whistle? Or say nothing?