The article isn't 100% clear on this, but to me it reads that the actual heat shield that they were going to use in the mission broke (not a prototype). Which is still much better than the alternative (losing a multi-billion dollar project in Rapid Unscheduled Disassembly)
Yep. Much better for the heat shield to break in a test chamber on Earth and have to be rebuilt, than for it to break during Mars atmospheric reentry and end the mission.
