What if the plumber missed a drain or supply by an inch? Guessing the robot doesn't adjust its outline. I.e. if a sewer stub is wrong by a few inches, the wall needs to be moved to fit the toilet, or the slab needs to be busted up and the sewer line relocated.
I suppose if it gets some of this wrong, it'll be obvious, and a human can correct it.
It can correct course due to deviations in floor surface or obstructions pretty well.
For example a pipe might not be in the location shown on plan for many reasons ranging from simple human error to a delta between the plan location when the pipe was layed and the time the robot got its data…keep in mind that when the pipe went in there was only dirt, not anything to accept ink.
But at that point it's back to engineering to figure out what to do (leave the pipe where it is and adjust around it _or_ move the pipe - possibly cutting concrete and perhaps untensioning/retensioning post-tensioned cables at substantial delay/cost) or move the piece of equipment that the penetration is serving.
One nice thing about automation like this is that the "as built" plans are more likely to be accurate because the only way to get "the computer" and "the robot" to stop squawking is to change the plans they are operating off of.
If this can't handle dirt surfaces, future generations/models probably will if there's demand. Perhaps such models would use spray paint/stencils or driving pins into the ground for marking purposes (or something more practical - I'm a software guy and this sounds like a hardware problem!).
My experience is with small residential builds but I would hope on large projects the location of each "unmovable" pipe/conduit etc that will end up penetrating a slab is already carefully verified before the next step is taken (such as placing concrete). Hopefully this is done with a total station rather than guys with chalk lines and tape measures. But a solution like this could reduce manual checking mistakes (of course, it's less likely to result in an experienced subcontractor noticing that the plan must be wrong because there's no reason for a conduit for 1KV electrical cables to come up 2cm away from a toilet trap in a multi-stall public bathroom - GIGO).
My experience is as an architect.
The CAD file isn’t the building no matter how much everyone might wish it were.
Even if the plans were the building odds of everybody using the same plan revision all the time is just about zero.
And most of the time, nobody is gonna pay for a super accurate as-built BIM. Because the point of the exercise is a certificate of occupancy.