The ipad WIFI only model does not have GPS built in
Apple has never explicitly stated why it does not include a GPS chip in the Wi-Fi-only models, but I suspect it is because many apps that use GPS for navigation and other duties need to draw on data from the Internet, even when they are out of range of a Wi-Fi signal. This means these GPS apps would effectively be "broken" when out of Wi-Fi range. That kind of problem is a no-no in Apple-land, and we can't argue with the reasoning.

Confusing the issue somewhat is the fact that a Wi-Fi-only iPad can fairly accurately pinpoint your location under many conditions. As long as the iPad can pick up even a few Wi-Fi signals, it can use Wi-Fi positioning - which draws on a database of known Wi-Fi hotspots - to determine where you are

So if you are able to use Waze on the WiFi only ipad it could be due to these external WiFi hotspots

Practically not feasible to use wifi only ipad for Waze due to all these constraints