I agree with your post most of all. It is true that the sound packet can be broken down into different harmonics, our brains also Hear what we hear by identification. On our TV we tried the sound repeatedly with the base and treble set at different points and my wife kept hearing the Y sound while I heard the L sound.
I am told that the recognition of the Y and the L are similar in our brains and we can “flip” this illusion in the same way that optical illusions can flip — for example the old hag and the young lady.
My high end hearing is so shot that a smoke detector can be beeping the low battery signal and I can’t hear it from 3 feet away. Of course that makes my wife frustrated. “You can’t hear THAT!!??”