This will pass your test because x != y, and the y != z term won't be evaluated since in C the '||' operator means 'or' and not 'xor'. But 011 doesn't strike me as something that should trigger a 3-input hardware XOR gate...
011 triggers the XOR because the code is testing for inequality which is simpler. For the XNOR, it tests for the equality condition which is simpler in that case.
EDIT: With the previously attached scripts, I used "random(0, 256)" for x, y, and z and even after about 5 minutes on the Arduino Due, there were still no invalid results on the print monitor.