this is an easy way to think of it. do the thumbs up. Bring your fingers slightly out of a tight ball so you can slide your racket in. Your thumb should be pushing on the back of the racket when your doing a backhand shot of any sort. This may be confusing or unclear but it makes sense in my mind lol
its not wrong its just a different technique. and my understanding through words may be different t your understanding in words. you can offer different advice and so can everyone else in the end it comes down to personal preferance with your comfort zone. and looking at that link and the pictures my grip is exactly the same as what hes doing. so get off my back.
usually thumb grip is used when the shuttle is significantly in front of you. For most backhand clears, depending on where the point of impact, one can alternate between the basic grip and bevel grip. If the shuttle has already passed you(say 1foot) then your thumb should be positioned on the side of the racket handle. badmintonbible is a good reference because it describes and depcits the few kinds of grips for backhand. In short, when shuttle is in front of you, thumb will be positioned near to or on the back (wide bevel), when the shuttle has passed you, thumb will be positioned nearer to or on the side (narrow bevel). hope that this video helps too http://www.youtube.com/watch?v=NSEL0V5RXwE and my apologies if i have made you more confused
Please note the highlighted portions in your post. You declare that the thumb should be "pushing on the back of the racket" for "a backhand shot of any sort". As briefly posted earlier - Wrong Delete the ''any sort'' and you'd be right in part. When attempting a backhand on a shuttle that has gone past you, the 'thumb-pushing-on-the-back-of-the-racquet' would be your immediate undoing. In such a situation, if you are to usefully retrieve the shuttle, you'd need to either grow an extra thumb on the other edge of the palm or follow what is shown on this page of the badmintonbible. (And do remember to see the picture from 'Behind'.) Also, I wouldn't want to be on your back. What you have there are 'raised hackles'