TEPaul,
I think you're right about the absence of early topos.
From what I've read it seems that the area wasn't conducive to survey work.
But, you're confusing "hollows" with "bowls", or at least not distinguishing between the two. and there is a huge difference.
For a bowl to exist I think man's hand may have been required.
While the soil may be good, drainage would be a problem, yet, I don't recall the bowls on # 16 being saturated after good rains.
Perhaps deep core samplings would assist with determining the origins of the spine and bowl features.
The theme of the entire hole is "punchbowl" , and I don't think it was confined to the green, I think CBM or SR had a hand in it.
You also have to remember that "spines" are a constant theme at NGLA, on the greens, in the fairways and roughs.