> Being hired in country A, for a company that has presence in both A and B, and then flying and working for a few months in B, could conceivably raise all sorts of flags if noticed.

My employer adopted a similar policy (just not as publicly announced as Airbnb's), and the way they work around this problem is by, assuming you reside in A, allowing you to travel and work in B but explicitly disallowing you from entering an office location in B.