I could be wrong but I don't recall anyone having said that - at least not as a general rule, applicable to all situations. Maybe in a specific instance you might say that the position of the hand is not the deciding factor but I don't think you can make a blanket statement to that effect.
I think what this provision is meant to convey is that the position of the hand cannot be taken on its own as the singular and definitive factor in deciding that a particular instance of handling is deliberate. I have certainly seen (and heard) people say that the decision can be made based on the position of the hand alone. It usually goes something along the lines of, "The hand (or arm) was in an unnatural position, therefore it was deliberate."
For me, the law is telling us that this is not necessarily the case - the position of the hand is certainly something to be taken into consideration but it isn't necessarily to be relied on all by itself - the referee still needs to decide whether the hand/arm is positioned that way as part of the deliberate act of making contact with the ball with the hand, or not. As far as I'm concerned, it's simply telling us not to be over-reliant on this one factor alone - you have to consider all relevant factors before deciding.