Why you say it is impossible?
According to ITU-T.
Distinguishable or not is a complete subjective matter with zero chance to actually prove something other than some basic stuff. One can say he is able to distinguish those tiny difference while others can say he cannot, whether he actually can distinguish or not. Who can prove?
Actually it's not subjective.
It's a simple A/B testing. When presented with a stereo song encoded with AAC 128Kbps and another lossless, without knowing which one is which, the listeners didn't prefer the AAC or the lossless version, i.e. they choose equally the AAC version to the lossless version. Meaning that there's no difference to the human ear.
Lossless is not always the best choice, as lossy is not entirely useless. For most pop music, and casual listening, lossy is enough, for a lot of people. Heck, I am listening to a J-Pop song right now, lossy iTunes format, and I am ok with it.
Pop music is the worst for encoding. Lots of things going on, lots of effects, I already explained it.
I admit I don't know a lot about audio stuff, signals and those related. But I trust my ear, and choose the best I can get to serve my ear.
Your guiding yourself