I think I have to come to the defense of Aussie, I think you're all being a bit rough and need not be...
First of all, this horse is a jumper (am I assuming correctly?) Jumper position is very, very
different from equitation position. Coming from the US which really has a huge equitation-nation (haha) I've shown for years in Equitation and know the jumpers fairly well. As a jumper - the perfect arched back, open chest aren't neccessary. Once you start getting up to the height that these fences are, it's really more up to the scope of the horse - and the rider well... getting out of the way essentially. Their job is to be light and springy like a cat - where as at the lower levels of jumping, it can be more focused on pose. I have to say that I have NEVER seen a professional jumper who has pefect equitation.
Also - yes, it does appear that his leg is a bit far back - but lets think about physics here for a second. Whether you like it or not, your leg is going to slip back a bit when a 1200 lb animal reaches over a 3+ ft fence. Unless your leg is tied down, for half a second, your leg will slip. I'm sure you all have photos in your home of yourself jumping - some have perfect leg position, some have it slipped back. I know I do - and depending upon the angle of the jump, the take-off, and how well the striding to the fence was done - your leg is either great - or slipped. Yes yes, gripping with your leg is the thing to do, and supporting your horse is a must - but to get to this level of fence height, I'm sure Aussie has proven that he has a decent leg :roll:
As for your release - it's just fine - your resting on the neck a bit, but I don't see that your horse is straining to get over the fence. Kudos.
Finally, before you all throw bananas at me for posting this, from the picture it appears that Aussie is a male rider. Women naturally have stronger legs - male riders often times pinch with the knee because it is well - more comfortable. I have seen many many male professional riders who ride with a pinched knee. It's just part of the sport.
Kindly don't light a fire under my bum - I'd rather like to keep it