Yes. Seems you now understand what the Joint Stereo. I would only add that the gain in the preservation of frequencies using Joint Stereo is far more important than a little more detail on individual stereo frequencies. Sound even at 320kbps mode Simple Stereo is empty (lost frequency) and clip-clopping. It can be heard by comparing the derivatives of each of the methods with the original matherial. It is better to use the latest version of Lame with maximum quality settings. Only so the difference will be clear. And these distortion arise on the low-quality encoder, and not on Lame.
Incidentally in AAC format but a heap of different innovative techniques used and the Joint Stereo. I hope you have heard how good AAC even at low bitrates.
And when using lower bitrate than 320kbps Joint Stereo effect is simply undeniable! At 128kbps bitrate and lower (even at 160, 192) Simple Stereo is different from Joint Stereo as heaven and earth.
I specifically re-checked this now. Used Lame 3.98.2 with the settings:
Joint Stereo:-b 320 -m j -q 0 --noreplaygain
Simple Stereo:-b 320 -m s -q 0 --noreplaygain
Joint Stereo retains much more frequency, the sound is softer and seems like more pleasant to the ear, and Simple Stereo Stereo stores a little more detail, but the sound of depleted frequencies and is well audible when compared with the original. Simply put, none of these methods at a low bitrate is not able to repeat the quality of the CD-DA, but Joint Stereo closer at him by the frequency component (which is pleasant to the ear), and Simple Stereo closer in stereo detail, but the frequencies are depleted.
And the difference with the original more audible in Simple Stereo.
To listen used Foobar2000 0.9.4.5 with SSRC Resampler Plugin (48000Hz) on Normal Quality in conjunction with Aureal Vortex 2 (AU8830A2).
Resampler is needed to remove distortions in the audio with AC'97 soundcards by means high-quality resample to the frequency of 48000Hz (internal operating frequency of AC'97 sound cards).
Although not exclude the possibility that someone will be more pleasant sound Simple Stereo at 320kbps. But at lower bitrates, Joint Stereo Advantage becomes more apparent.
By the way here you can hear the difference right now:
http://etn.luon.net:8100/
http://etn.luon.net:8200/
Share where you got such an explanation, please.