Engine diagnostics in 2000 GTP

I have a 2000 Pontiac Grand Prix GTP, and the engine seized while we were driving it down the highway. Before it got to the current shop, we were told the alternator and supercharger were okay, but the engine didn't spin.

We haven't authorized any repairs, but the shop has completely torn out the engine. Would this be considered a normal part of the diagnostics? Tearing apart an engine seems a little extreme to me, but would the shop be able to argue it was necessary for diagnosis?

like the engine is out of the car?!?!? no that is not necessary to diagnose the prob., to the best of my knowledge. maybe what they meant is the engine is all torn apart, but still in the car?