Seems like a lot of effort for an edge case. Now you've added a dependency on some network service you need to access (and from WhatsApp's POV: maintain) before placing outgoing calls. If you use GPS instead, you're dependent on having the location permission (which is not needed to run WhatsApp in general), and you're draining everyone's battery and adding latency to get a sufficiently accurate location lock. Doesn't seem like it would be worth the trouble to me.

There would also be a number of people complaining loudly, demanding to know "why does WhatsApp look up my exact location [using the GPS] at the precise time I make a call!?".

Good luck convincing them that the location is not being logged permanently by WhatsApp servers -- or even sent to them in the first place.

I've never been to Saudi Arabia, but in the UAE and Oman if you were to receive a WhatsApp call using a foreign number from a free country, lets say France, the handshake for the call would still be dropped with the attempted call failing.

On iOS, you would get an error saying "Call couldn't connect. X's mobile carrier or WiFi doesn't support WhatsApp calls".