It's actually a really good feature. As you know the thrust levers are set to the "climb" detent for everything but takeoff and landing, and with two engines operating represents the range at which the FADEC will control the thrust between idle and climb thrust depending on the vertical mode selected.
If the pilot disengages the autothrust then the FADEC says to itself "ok, you want control of the engines so here you go" and the thrust moves to the thrust level corresponding to the thrust lever angle. If the thrust levers are in the CLB detent then it gives you climb thrust, move the thrust levers back and the thrust behaves normally and decreases according to thrust lever angle.
If the autothrust has an uncommanded (by the pilot) disconnect rather than give you a thrust rating you probably don't want (CLB Thrust) it freezes the thrust at the level it was when the autothrust disconnected and warns you about it. All the crew has to do is take over manual control of the thrust levers like they used to do in airplanes with servos instead of thrust lever detents.
Yes, it's an ECAM action that is prioritized down the list, and ECAM discipline is drilled into every Airbus pilot so they might not actually get to that procedure until a little later. But a little system knowledge goes a long way too. Simply moving the thrust levers forward would have made their life a lot simpler. That is not a criticism, just an observation.