Hissing most likely comes from media, unequal discharge rate is legit problem. I'm not an apple fan but when it comes to reliability major brands at least do some product design and quality checks, meanwhile most chi-fi IEMs have options for MMCX connectors that are entirely unsuitable for the use case and should have been shot down during the design phase, but hey - "the more options the better".

P.S. For anyone thinking i bash just because of China or western audiophile superiority - no i just got burned by articles like this and crinnancle reviews twice and sharing my experience.