He is talking about how he noticed the coupling capacitors on the Pico Slim and decided attacking something for being designed properly would be the best new strategy. Those coupling capacitors, IMO, are a much better idea than a virtual ground capable of only 25mA current that that the audio signal also goes through. It all depends how you visualize the schematic...one side of the headphone driver is connected to the amplifier, the other side is connected to the virtual ground (or a real ground, or inverted output in the case of a balanced amp). Something to think about whenever an amp claims it can output 250mA of current...
By using single supply (no virtual ground) and coupling capacitors, there is a true low impedance ground which is the battery negative terminal. The capacitors I am using are new and not cheap, electrolytic capacitors of appropriate size would be too large for a thin portable amp.
There is much more but that can wait until both of these products are in owners' hands.