Nope. Never heard of this diagnosis. I think most of us who are mild are thankful that we ARE mild today -- but we are aware that this might not always be the case.
In terms of your lesions not being classic for MS, yes, MS CAN present itself less typically and this does make a dx harder.
One other thing I will add though, although NOTHING is definite with this disease, it is generally thought that people who experience sensory sx at the outset (as opposed to motor problems) will have a more mild course. (But even then, there are unfortunately no guarantees.) I believe that this might be what you're doctor is going off of but as far as a "sensory" dx, never heard of it. If you find out more about this "new diagnosis", please let us know and of course, do keep us posted on your situation.