I don’t imagine that the builders planned for people climbing on the wall, you aren’t worried about it coming out of place?
Though this is certainly a consideration, in this case no, from what I can see and feel when fingering the rocks at lower levels the wall is actually built quite strongly and the rock pieces seem to be held firmly in place (not that it's out of the question maybe a smaller piece might come out).
Insofar as surface quality buildering is often safer, more dependable than out on real rock. Also when climbing w/o ropes you habitually try your best to make sure that if any of your points of contact were to break off (or you slipped), you'd still be able to keep yourself on the wall with the other 2 or 3 points of contact.