|Special Collections, John D. Rockefeller, Jr. Library, The Colonial Williamsburg Foundation.|
It makes sense. Both tents and sails are canvas after all. There was a detachment of sailors serving the guns and building entrenchments during the Siege of Yorktown and it is possible this was the shelter for some of them.
Prior to Apple's discovery, I had assumed that sail tents were a last resort of shipwrecked seamen. When Brinton Hammon's vessel was stranded on a reef for two days in 1747, his captain ordered the crew to row ashore with 'our Arms, Ammunition, Provisions and Necessaries for Cooking, as also a Sail to make a Tent of, to shelter us from the Weather.' Daniel Defoe wrote a similarly desperate decision for his fictional Robinson Crusoe in 1719:
Having got my second cargo on shore...I went to work to make a little tent with the sail, and some poles which I cut for that purpose.
After the Duke William sank in December 1758 with hundreds of Acadian refugees aboard, an anonymous author penned a letter to the The Gentleman's Magazine suggesting that all captains should be prepared to create rafts for 'preserving the lives of the persons on board in such a case.' In this, the author suggests that the crew load the raft with provisions and 'a spare sail, to serve them for a tent' should the survivors reach shore.
 Fuss, Norman, 'An Iconic Artifact Revisited,' Journal of the American Revolution, January 13, 2015, accessed May 27, 2019, <https://allthingsliberty.com/2015/01/an-iconic-artifact-re-examined/?fbclid=IwAR1v7GtcZ-0Rt4A9YsmpO_5PLwOIulVlSEvCee0X5ljHQI6MrxchpNfgVi0>.
 Hammon, Brinton, A Narrative of the Uncommon Sufferings, and Surprizing Deliverance of Briton Hammon, a Negro Man, Boston: Green & Russel, 1760, page 5, via Documenting the American South, University of North Carolina Chapel Hill, accessed May 27, 2019, <https://docsouth.unc.edu/neh/hammon/menu.html>.
 Daniel Defoe, The Life and Strange Surprising Adventures of Robinson Crusoe, Vol 1, London, 1784, via Google Books, accessed May 27, 2019, <https://books.google.com/books?id=v31dAAAAcAAJ&pg=PA54&dq=sail+tent&hl=en&sa=X&ved=0ahUKEwim5cm3pJPhAhXPtlkKHS9tDFIQ6AEILzAB#v=onepage&q=sail%20tent&f=false>.
 Anonymous, 'Hint to the Captains of Ships to Provide Against Accidents,' The Gentleman's Magazine, Volume 29, London: D. Henry, 1759, page 58, New York Public Library via HathiTrust Digital Library, accessed May 27, 2019, <https://babel.hathitrust.org/cgi/pt?id=nyp.33433081674107;view=1up;seq=70>.