1. No. OP's friend is due nothing.

2. TSA checks passports for ID purposes only.

3. Carriers do check passports (and other docs) because they are liable to a significant fine and all of the costs associated with repatriating the pax if he is denied entry based on insufficient docs.

4. IDB applies to oversold situations only. Urban myth to use it for other stuff.

All it takes is for one pax on that carrier to have been denied entry somewhere in the EU based upon a torn or otherwise loused up passport and it's easier to offload the pax than to run the risk.