Hi Dave,
I could be wrong, but I believe that's a part/template specific setting. When you create a new part, you're essentially setting up your units at that point. The dialog should state which units each choice will be using.
I don't believe Sketcher dimensions are exactly like Drafting dimensions in that particular regard.
Tim Flater
NX Designer
NX 9.0.2.5 Win7 Enterprise x64 SP1
Intel Core i7 2.5GHz 16GB RAM
4GB NVIDIA Quadro K3100M