You sound like a safety officer!Using an example here to bring in the element of 'risk'.
A defender under absolutely no pressure is trying to chest a long ball in his own PA. He does so with his arms well wide of his body. He misreads the flight of the ball and the ball clearly strike his arm. Everyone expects a pen and a pen is the correct decision. Leaving the considerations aside for the moment, this is not "a deliberate act of a player making contact with the ball with the hand or arm." He has no reason to do this deliberately and give a penalty away. But he took an unnecessary risk and he is paying the price. In this case the "unnatural position" consideration is what determines the deliberateness of the act.
The OP is not as clear cut as my example and its a case of YHTBT. But from the description the considerations that I would use to make the decision is:
Does the player attempt to avoid the ball striking his hand/arm?
Is the hand/arm moving towards the ball or is the ball moving towards the hand/arm?
Since when did the laws consider risk?
This I'd expect from players.
It's all about deliberate handling of the ball, either you think it was or in this case think it was not.
I wasn't there, only the referee's opinion matters.