Why should you add dry mix to water and not the other way round
Yes, there is a very good reason.  If you add water to dry mix in the bottom of the container, you get a nearly impossible to incorporate glob of the dry mix at the bottom.
On the other hand, if you add it from the top, it's much easier to get it all incorporated.
This works with everything from pancake mix to drywall compound.
Try it each way and you'll see for yourself.