Here in Florida where OC is illegal, if you have your gun in an IWB and take your cover garment off, so the only concealment is the part inside the pants, then LEO is going to consider that OC and you will be in hot water.
The standard here is "normal sight" and most individuals seeing a half exposed gun will recognize it as a gun with "normal sight" hense it is OC.
My bet would be that Michigan is the same.