Shaped upper rock of rock-on-rock

I have toyed with the idea that the upper rock in a rock-on-rock structure could be deliberately shaped and representative. This weekend, while wandering around between Brown Rd and Jacob Gates Lane in Harvard, I started noticing one after another example of rock-on-rock structures with a kind of off-center "Manitou stone" shape - as shown above. Unfortunately, I was camera challenged and came away with only one decent picture for my efforts. Please imagine lots of other examples (six or eight) that used this same shape. I called the shape a "boat rudder" in my little book, where I constructed a fanciful argument as to why it might represent a heart.

Be that as it may, the idea that the upper rock might be deliberately shaped makes sense. In this next example it is very hard to imagine that the person making this structure did not notice the shape of the rock.This looks like a bird. Maybe the off-center Manitou stones shape represents a bird too.

There are lots of examples of rock-on-rock structures where the upper rock is a simple block or is made of a nice veined material. There is no reason to think the shape is important. Sometimes rock-on-rocks seem to line up and shape would play no obvious role in that function. So I do not think there is any deliberate shaping going on most of the time. But it is worth paying a little attention to when examining a rock-on-rock.