(This is an extension to my proposal for the NetworkInformation.type enum at w3c/netinfo#9 to cover edge cases. Licensed as CC0 / public domain.)
The Network Information API is designed to allow websites / WebApps to change their behaviour depending on the type of connection their device has. Discriminating by whether you are currently connected via WiFi or 3G, however, provides a footgun to developers: E.g. when you are roaming and tethering to your smartphone but your device indicates it's on a WiFi connection, you may assume that the user is on a high-bandwith, low-latency, low-cost connection