Not necessarily. Most MCC discs are made both in Taiwan and India, and they do much better in accelerated aging tests (humidity, heat and UV light) than TY media.
@the original poster:
As DrageMester explains, a sinking test has no relevance whatsoever in real-world and is plain useless. It only tells you that water do or doesn't damage the discs, and tells you nothing about what air humidity can do. Air humidity is water vapor, which is a gaz, not a liquid. Water vapor can penetrate polycarbonates much easier than water can, due to different molecular properties. These different properties are what allow exterior wall treatments to reject water (rain) but allow vapor to go through. Vapor can aso carry contaminants that water can't.
Besides, some heat is needed to "trigger" the accelerated degradation due to moisture.
Last but not least, dozens of controlled experimentations show that moisture does affect the degradation of discs. These are accelerated aging tests, performed both by manufacturers and independant organizations. With most MIDs, the degradation induced by high humidity in real world can't be properly detected without professional equipement, and not in a short period of time (less than 2 years) anyway. Acceleration through heat is needed to measure degradation on shorter periods of time.
So performing a non-controlled, isolated experiment with no professional measuring equipment, showing no actual data (PIE/PIF scans at the least) and simply stating that humidity can't be an issue, is plain nonsense. Sorry to be kinda harsh, but spreading misinformation based on sloppy and amateurist experimentation is not gonna help anyone, and I'm not gonna let it stand.