I presume that the angled shots were added to try and take the shooter out of their normal 'comfort zone position' to add an extra element of difficulty?
... but you can use a Black and Decker workmate under the fore end ... so your position can stay pretty much the same and the workmate is adjusted to get the angle.
So over 15 yards and 15 degrees just adjust the workmate and aim inside bottom of kill.
Sounds good if you have shares in workmates, otherwise it just seems like a way of getting those wanting an edge to buy a workmate. When everyone has a workmate it seems pointless having the angled shots.
Sorry I'm new, so I'm probably missing something obvious.