Same problem here! Using 2.79. Makes no sense and definitely frustrating. This is a recurring problem throughout the entire shader forge course, especially the "Bodies of Water" one. Whenever Kent uses a rotation in the Mapping Node, expect problems if you're running a Blender build other than 2.70. You're going to have to do a lot of tedious tweaking to get the rotations to match the videos. :(
Sorry to hear about confusion in this thread. I still use the same techniques for shading and node network construction as I did in these lessons, so I'm not quite sure where the disconnect is happening. One thing I will say is that the information to learn is not the exact values I plug in. Rather the concept of how to tweak the values is what I hope you learn.
In practice, I don't memorize certain values for the mapping node. But I understand how the node works and thus how to go about tweaking the values to my needs. I think that's why the nodes seem to function the way they always have to me, even if the underlying math was changed.
Does this make sense?