A guy I know is a maintenance engineer for United.
He claims to me that the mere characterisation of the engine failure (compressor stall, large flames with sparks, high EGT at idle...) should have been enough by itself to convince the crew to land.
He seems to posit that the crew could not know the aircraft was not suffering from some latent damage and that this is the basis of the FAA's ire.
I am interested to hear responses to this.