That's not a failure like the E46 though. The real problem with those was that the flap spindle would break and the engine would eat the flap and the remains of the spindle. Thus - mashed valves, cylinders, pistons etc. Often a new engine fix. Sometimes get away with replacing the head, the valves, the piston and some other bits.
The post you link just seems to suggest that the flap leaked or that a gasket went or something. Tbh, that's just on par with any car where anything can go wrong. Had the flap broken off and the engine got mashed, then we might have an example.
As such, I still stand by my guns that there are no reported swirl flap failures on the E9x. Willing to be corrected tho.
MY14 Space Grey F11 530d M-Sport