just curious, the brakes did work and you were able to use the foot brake to slow down but with diminished braking, is that correct?

I would take a digital camers to the dealership and photo the ruptured line they are talking about. surprise them. And tell them you are going to file with NHTSA, which you really should do.

Brake line failure by rupture is probably the number ONE most extensively tested item done in vehicle development.

Even in off-road conditions anything that could possibly rupture a brake line is tested. Have you ever seen how brake lines are integrated into the chassis to prevent hang-up?

When did you have your brake pads changed? Unless you drove the front brake pads to death and drove on backing plates to cause heat related failure I cannot imagine how your failure happened.

You should also inspect that the ABS unit somewhat proximal to the power steering pump to make sure it wasn't damaged during the last service.

The ABS unit has a series of circuitous brake lines emerging from it to act as a damper against vibration failure. If a tool got hung up on them and damaged them in a previous service, maybe that occured. But that is unlikely and a tech would have reacted to that, still worth checking.