REALLY? BROKEN FLYWHEEL?

You need to talk “tranny” with them.
Let them know there was a big shutter before the noise. Rattled your teeth. Then you lost power and “bang.” Let them know you are blaming the transmission locking up on the highway and you know that cracked the fly wheel... I mean if they did the transmission and they forgot to inspect a 248k flywheel? It had to crack from all the in and out of the transmission. Your lucky your not hurt.
Also mention your uncle works for the department of motor vehicle and he was concerned for your well being. You guys are close- fishing buddies.

I rebuilt a lot of GM transmissions when I was a dealer mechanic. Saw lots of stuff and fly wheels break for two reasons. Loose bolts or stress from engine or transmission failure or driver induced failure (roll back burnouts, rev drive drops or fwd to rev like in the movies.)
Joe