plakat
Headphoneus Supremus
3.5mm TRRS plugs have the two grounds adjacent. If you plug them into a single-ended headphone out that doesn't support mic/controls, the two grounds will both connect to the jack's ground. If the device supports controls (like an iDevice or android phone) then one pole will be for the controls and you will only get one channel. I have tried many DAPs and amps that don't support controls and they usually work with balanced 3.5mm TRRS headphones. This is not true for the AK 2.5mm TRRS because it orders the signals differently.
Having a TRRS fit a TRS jack so that the second ring and the sleeve both connect to ground is more luck than anything else I'd say: just take a look at the numerous reports on TRRS headphones (with mic) giving problems with some players. But nice if you were lucky in that regard... I'd just not take it for granted.
Plus you're correct that this lucky case can only happen if the balanced TRRS headphone is wired with the two grounds on the second ring and the sleeve.