You've got me there monk. While I have seen villagers pick up boulders when exercising (not my form of fun exercise but hey, to each their own) I have never seen them take the boulders anywhere!

Nor have I seen a villager say they are doing a task but do something different. You have a new glitch there.

BTW, how do you do those screenshots (on a PC). I was trying to get one for another glich but aparently not computer savy enough.