Earlier quoted context omitted.
These things don't look very powerful, to put it mildly. GPS means outdoors which means wind which is a bit harder for a small, light hovering robot to handle. Indoor lets them demonstrate the principle with a useful simplifying assumption of no wind.
Did you watch the same videos I did? They have these things lifting sizeable pieces of 2x4's ( https://www.youtube.com/watch?v=YBsJwapanWI ) and they pull of some pretty absurd manoeuvring ( https://www.youtube.com/watch?v=MvRTALJp8DM ) and recovery ( https://www.youtube.com/watch?v=geqip_0Vjec ). Navigational issues resolved, I have a hard time seeing these things having trouble with a modest wind.
A constant wind I agree looks like it would be within their capabilities, though their route planning software would need to take account of it and approach the target from upwind by default - not impossible but another thing to account for.
The real issue for me is gusting. They are definitely small and light enough that power-to-weight issues, particularly when carrying a load with a higher surface area to the wind than the craft itself, means that it will get knocked off course by gusts. That obviously needs allowing for when navigating to and from the construction site, but particularly when dropping off a load - if the release comes at the same point as the gust, the part simply won't end up where they wanted.
Do I think all of these problems are unsolvable? No, but it makes a useful simplifying assumption for their version 1 that they don't have to deal with any of them because they're flying indoors.