Trust me, I've seen it happen, paralleling voltage regulators can lead to oscillation and complete board
destruction. Why risk that?
Thermal and over-current shutdown cannot protect against it, its an over-voltage problem. And yes the
regulator isn't destroyed, just the rest of your circuit.
A single regulator is stable (with the right capacitors and a 'passive' load). With two you have to do the
network analysis using S-parameters or something to convince yourself a particular setup is stable
rather than a high power oscillator circuit - two high gain amplifiers fighting each other basically.