How many minor hilltop sites do we have to see before detecting a pattern?

I went for a drive and walk last weekend and took a colleague from work. We went up to Townsend State Forest (which looked interesting the last time I was exploring topo maps at Topozone.com.) So we walked up the dirt road. Somewhere around where I outlined, there was a level shoulder with a site taking advantage of the fine view to the southwest. The type of site with simple piles and rock-on-rock was a lot like other sites seen recently on other hilltops - the one in Sterling, looking west to Wachusett, the one north of Andover on Poplar Hill looking northeast. It is also not too different from what is on top of the Hill of 500 Cairns (also here). In addition to this site being similar in topography, it also had similar preponderance of rock-on-rocks and simple low rock piles.

As we were walking up the road, I was looking to the right and the guy from work was looking to the left and saw a rock on rock. We went over to take a look:
Just beyond it, on the western side of the ridge, were a few more small piles and wedged up rocks
One became aware of the view of the sky. If the trees were not in the way it would be a complete sweep of the southern and western sky. There were some hills to the west forming part of the horizon. As we continued a little higher, within the site, the piles got slightly more substantial:
Here were almost three in a line.
However my idea that these represent lines of sight is a bit contradicted by the fact that the piles were not all on the same side of the ridge. Before we abandon this idea though, note how many of these piles seems to have a rock sticking up higher than the rest, like marker piles. (See also here).

This next one was to the east. This is probably the most substantial pile we saw over at the site; and from there we continued uphill.
At the next level spot we were back to simple rock piles and rock-on-rocks.
Here is one last one from up there:
A beautiful bright day. After a while we headed southeast back down the hill...