I would suspect that John was the son of Samuel, or perhaps a nephew. If so, it would seem that he was furloughed or transferred and the mustering officer erred in his muster roll entry.
John W. S. Leslie enlisted as a Private in Company F, 32nd Arkansas Infantry enlisted June 16, 1862 at Burrowville by Sam'l Leslie, deserted January 17, 1863
Sam'l Leslie, elected Captain on organization of Company F, 32nd Arkansas Infantry, at Burrowville October 2, 1863, date of commission June 16, 1862, age 50, born in Tennessee, appointed from Arkansas, resignation accepted by Lt. Gen'l. Smith October 2, 1863
32nd Regiment, Arkansas Infantry
32nd Infantry Regiment [also called 4th Trans-Mississippi Regiment] was organized in the summer of 1862 with men from the Fayetteville area. It served in McRae's, Churchill's, L. C. Gause's, and Roane's Brigade and fought at Prairie Grove and Helena where it lost 17 killed, 46 wounded, and 26 missing. The unit went on to take part in the conflicts at Bayou Fourche and Jenkins' Ferry, then in March, 1865, disbanded near the White River. The field officers were Colonels Lucian C. Gause and C. H. Matlock, Lieutenant Colonels William Hicks and C. L. Young, and Major Arthur F. Stephenson.