The Moondrop MIAD 01 is one of the most distinctive Android devices of 2024 thus far. It has a 4.4mm headphone jack to go with the more conventional 3.5mm type. Furthermore, it seems it might be as appealing to teardown enthusiasts as well as audiophiles, and may, therefore, also be easier to repair than most modern smartphones.
Your experiences were correct, don’t doubt them. That would have been ground-referenced equipment, ie plugged into wires that eventually join a wall. RF interference would interact with that quite differently, unbal vs bal would be quite different.