I don't think Sony is lying. Output power depends on maximum voltage, current and output impedance of the amplifier. This being TDA amplifier the input signal for measurement has to be digital and would be 0dBFS. You can't equalize a 0dBFS anymore since it will start clipping. If you feel the output power is low, blame the various health laws that limit max. output power to be around 85 dB SPL in the earphones. So, from the average sensitivity of an earphone driver, the maximum power required is calculated. Even a $0.50 DAC can deliver enough power to blow your ear drums out. The power is limited to protect hearing and also the drivers in the earphones. What could be done is to measure the impedance of the earphones and adjust power accordingly. Most modern audio chips detect the impedance as soon as you insert the plug into the headphone jack. I use this feature to measure the impedance of my earphones to check L/R balance. Some android phones(Axon 7, LG G6) already do this I think.