On TRRS there are 2 types-
1. The original TRRS configuration was created by Nokia and has a pinout of Left Audio, Right Audio, Mic, Ground.
Apple came along and in typical elitist fashion changed their pinout to Left Audio, Right Audio, Ground, Mic.
This is why many apple headsets will not work with android, because the last 2 connections, for Mic and Ground are switched. The issue is with the hardware.
The way that songs are skipped (forwards, backwards, and pause) occurs by sending signals down the ground channel (when you tap the button it shoots an electrical signal that the phone will pick up and interpret).
The way that volume is increased/decreased occurs by sending signals down the Mic channel.
This is why- if you try a set of newer iPhone earbuds on the GSIII- as I have- the center button does nothing, but yet the volume up and volume down both pause tracks, and allow you to skip them. The same happens with Xperia phones, which uses the original standard.
Additionally, Apple has patents on their TRRS connection- in fact on the resistances (the actual ohm resistance in-line on the controls- not to get scientific or anything ) so that the headphones are designed to work only with Apple products. In other words- you could have a device with the same TRRS Pinout as apple products- but the headset wont work because the resistances (ohms) of the headphones send signals that your phone is not allowed to interpret into the correct actions (since apple patented these)
The problem is that nowadays MOST headset manufactors use the standard compatible with Apple, because they were the most succesful smartphone makers for some time, and thus it made sense in a business point of view to have a larger addressable market.
Some other phone manufactors stop using the "original TRRS" standard because of this problem. So now most smartphones support the pin-out developed by Apple.
Xperia phones unfortunatelly use the original TRRS which now become the less common standard used by the industry. So MANY headsets have problems on Xperia phones.
By the way the original standard is called CTIA and was developed by NOKIA, the new one is called OMTP or vice-versa, i always get confused.
Hope this clarifies things up a bit
