This is indeed one of the reasons. Theoretically, when you query O365 you would get the closest one to your area. Your request would go over the internal Azure network and still be very decent in speed. Their internal network is impressive.
However, some companies might query it from APAC but the proxy or router or whatever is located somewhere else which already causes the delay.
Last but not least, O365 has made throttling limitations which can only be lifted by contacting MSFT support. It is also described in our documentation