Not that I disagree, but I want to confirm: you are suggesting the reason (or one of the reasons) they chose to do stone carving, as opposed to some other form of monastic pursuit, was because it took a lot of time and effort?
A great deal of monastic pursuit was in the interest of slowing down, focusing, applying one’s entire self to something, and recognizing the greatness of god and creation, so yes, anything that encouraged focus and contemplation would have been privileged on those merits.