IP addresses tend to have a relatively long lived association with a subscriber, often weeks. So an app which communicates out the wifi names naturally reveals

IP addresses tend to have a relatively long lived association with a subscriber, often weeks. So an app which communicates out the wifi names naturally reveals the IP address (unless there is carrier NAT, i.e. on mobile, in Russia). So with a database of such information, the IP also reveals probable wifi names and hence location.