Inaverdant Whistle

[Smoke]

Watching a high school girls varsity game last night and Team A had the ball then A1 and B1 got to the floor and they tie it up briefly and the offical blows his whistle softly so Team B lets up meanwhile A1 grabs the ball and throws to a wide open A2 who scores. Team B coach ask the official about the whistle and the official says oh it was inadverent. I thought on this type of play they whistled the play dead? Who is right