That said, the machines are in field use, since masons are scarce and expensive. You're right about the big jobs, too; they're apparently pretty much limited to sites like universities and hospitals which have lots of big, featureless walls. The Tech Review article about it is much more informative than the NYT one here. [1]
I think this sort of automation worry seriously over-generalizes from factory robots. Robots are spectacular at doing repetitive tasks with nicely-arranged inputs and fixed workspaces. Hence, Amazon warehouses and Ford factory floors. But (as the SAM people admit) outdoor, new-worksite tasks are going to involve way more mixed human/robot tasks.
[1] https://www.technologyreview.com/s/540916/robots-lay-three-t...
On one hand, fresh mortar can clearly support several new layers of brick as a wall is laid. On the other, common estimates suggest a 24 hour wait to reach 60% of final strength. How light would an on-wall robot have to be to work at a steady pace without disrupting the still-drying brick?
The other question, I suppose, is whether the brick-supplying robot makes that redundant. It's either going to need a scaffolding or a cart/flatbed that moves frequently to keep feeding target that moves back and forth, and if you need a ground-supported robot arm right near the wall it might just be easier to do everything that way?
There is no technical reason why the end user couldn't map out corners and turns in a CAD program. I think it is a physical limitation because the Bot is so large.