Pondering the meaning of "comma" shaped stones

These are from the Marble Hill Conservation area in Stow, MA.

Two pictures of the same thing using the new camera.
Note the parallelism between the support rock and the upper rock. I remember seeing this next one last time I visited the site. I do not think this is the same kind of thing as the "comma" above.
But this next one does seem to be the same idea as the first example above.
I have seen this pattern a number of times before. For example, this one from Flag Hill, a different Stow conservation land:
Seeing this enough times, I think the shape is worth trying to interpret.