I wish I had the answers to both of your questions and observations. The answers would be interesting pieces of family history. However, the reasons were not passed on, either by spoken word or written.
I believe that two of his brothers served in the CSA. One was Edwin Ruthen Sawyers, who served in 21st Mississippie Cav and in the 9th Mississippi Inf. He was a private in both units.
The military service choices resulted in a several interesting but sad circumstances in the family history.
First, Edwin and his family moved to Texas after the Civil War, settling in Limestone County, around the Waco area. While John M. remained in Tenn., his son William R., migrated to Tarrant County, Tx. Neither uncle or nephew had an contacts with each other.
The second is my grandmother was a Sawyers, who married the grandson of Frances Hodo Gardner. Since her grandfather was a "damned Yankee", she was an outcast in the Gardner family.