There was another William Hutchison in Loudoun County, Virginia, in the late 18th century. When searching at Ancestry for William Hutchison, see in "Stories and Publications," this book: James W. Head. HISTORY AND COMPREHENSIVE DESCRIPTION OF LOUDOUN COUNTY, VIRGINIA. Washington, D.C.: Park View Press, 1908, p. 135. The entry states that a William Hutchison was commissioned as an Ensign in June of 1781 and that he was a son of Benjamin Hutchison.
This was not William Hutchison, born 1715, as he was about 66 years of age in 1781 and too old to receive an officer's commission.
The book was also published at Provo, Utah, by The Generations Network, Inc., 2005.