It literally has no idea that the pauldron is going to reveal its position, not to mention haste is really the only thing that matters to the Pater if it wants to avoid being perforated with chain-gun rounds. The only information one has to go on from your post is your character lunging to the right and throwing its weight to the side, neither of these things suggest it leapt clean over the pauldron, therefore one can assume that the Pater made some contact with it before it left the Mech, because it is there quite clearly in the picture and that's the direction you chose to dive in, without any mention of your character sailing clean over the pauldron with no contact. 

You can either accept that you should have mentioned the pauldron, as regardless of how meagre an obstruction you deem it, it is still a very obvious one and one that bears mentioning at such a crucial juncture, or you can ask for Pollen again and see if they feel Higan detecting the Pater leaping off his mech's right side was unfair. 

Once again I should point out your character carries out another flawless action after another flawless dodge, you suggest it's lithe and agile without a medium of panic, and yet its ribs are broken and its lower stomach stuck to the top of the Mech, which hardly suggest to me that the escape should be as perfect as you describe.

My tiger example was to explain how Higan would feel the weight of the creature leaping off from inside the vehicle.