A number of architectural factors go into whether or not there is a "scoop" there, or even a need for one. One of the biggest is the combination of breech size, and the size and placement of the lock, height wise, on the side of the barrel.
With a larger breech and the lock placed low, the transition of metal to wood at that oblique flat flows almost in continuous manner, such as in the photos. In other words, the slope of the wood matches, or nearly matches the slope of the flat - No Scoop at all.
In the opposite situation say a 13/16" straight barrel and a full size Siler lock or, for the sake of example, an even larger lock such as Chambers Early Ketland, the difference between the slope of the oblique flat and the wood directly behind it becomes much more pronounced, and thus the little scoop is used to transition from one to the other.
Sometimes the architecture is such that a gentle taper from one into the other works, but other times such a taper would obliterate the top of the lock molding just behind the barrel and therefore won't work.
That's my take it...
Jeff