During the Spring of 1865 Major General George Stoneman took his forces stationed in East Tennessee into North Carolina and Virginia for one last thrust to completely eliminate Confederate resistance in those areas. Even though East Tennessee had pretty much been cleared of Confederate forces it is quite possible that the 4th Michigan was used here to replace units that moved with Stoneman and to keep a balance of Union troops in the area.
Maybe someone else has mre definite info and will comment here.