Your neurologist is using due diligence in performing a series of test to rule out (or in) a mimic of multiple sclerosis.
A high ACE test would be a red flag away from multiple sclerosis as a diagnosis, and towards one of the mimics.
However, an actual diagnosis is best left to your neurologist, because the picture is more complicated than a single test and only your neurologist has all the information available in your specific situation.