I could not disagree more.
The simple fact of the matter is, we as individuals, are all hugely different. Everything about us is different from our personality to our body and thus, how can one way of doing things be right for everybody? Taking an extreme example to demonstrate my point, think of the Flamenco technique 'picado' ie fingerstyle equivalent of alternate picking. One alternates between picking with the index and middle fingers. Now what if a guitar player wishes to learn the technique but is missing an index finger? He adapts and plays the same thing with his middle and ring finger (obviously on the right hand, assuming he's playing right handed guitar). If it sounds exactly the same and is efficient, how can one say it's 'incorrect'?
I don't get your criticism of vibrato as you're saying that blues guitarists are incorrect, as the correct method is to vibrate from the wrist?
'Correct' vibrato is achieved via a means of rocking your finger from one fret to the other, but remaining within a semitone gap. This achieves the effect of altering the pitch of the note both lower and higher, rather than just higher which is what happens with blues vibrato technique. Eric Clapton doesn't 'shake the whole neck' as you put, he rocks the string up and down, ie he pushes in the direction of the strings either side of it. Not 'correct' vibrato technique, but it gives a great sound and is efficient, so what's wrong with it?
I'm extremely critical about my playing and technique, but I would never inhibit myself by learning a factory technique that doesn't feel right for me. Efficiency is king for me, and that is attained via quick, easy and comfortable technique, regardless of whether it's traditional or not.
As for the second paragraph, yes, the technique of keeping your thumb pressed against the back of the neck is 'correct' technique. My point was that I disagree with that and thing that it's ridiculous thing to do so, as you're eliminating a whole digit from the guitar neck. Obviously there are times when the thumb is not needed and it maybe more comfortable, or efficient to keep it behind the neck, but my point is, everyone is different. There are some chord voicings that I quite simply would be unable to play if I didn't use my thumb. I would have similar problems playing bass lines under chords and melody if I didn't use my thumb. And for the record, I can produce any vibrato that you wish with my thumb bent around the neck.
But ultimately I'm saying, everyone is different and do what's best for you!