Genuinely Confused About Rule.

Okay so I’m watching Packers and Falcons. There’s a review to see if it’s a pass or fumble and the commentators say “let’s see if his arm is going forward” the ref in the booth says “his arm was going forward” and then the ref on the field says it’s an incomplete pass cause the quarterback’s arm was going forward. Okay so I feel like this is the way the rule has always been. Why the hell in our game was it that if the arm is going up at all it’s going forward? I keep hearing that the rule was applied correctly. I realize it’s easy to jump to thinking they’re just trying to screw us but genuinely asking, is there some weird specific type of play in our case where it’s a different rule? I just don’t get how still everyone says they applied the rule correctly to us but everywhere else it’s not just that the arm has to go up.