My company moved ~5 blocks and it really screwed up the map on my phone (which I use to get around the city) for several months. My company had left the network SSID the same in the old location, so that no one had to re-configure their wifi. Even with GPS on, my phone was always convinced it was in the old location up the block, and this would persist even when I was out on the street, until I walked around a bit.
There are companies (presumably Skyhook is one of them) who drive around mapping SSIDs to physical locations. The problem is that SSIDs can move or be duplicated elsewhere.
The article says of one of the couple "at one point he reset their router, and changed the frequency at which it broadcasts; it didn’t solve the problem." It does not say if he changed the SSID.
Theoretically, location is often determined using not just one but several nearby SSIDs, a sort of triangulation. Another possibility here is that there are multiple nearby SSIDs around this home that match the SSIDs surrounding some other area tied to the victims.