That's just a bit of spin. There was a conscript law in effect at the time but in the records he is not listed as a conscript. In other words he wasn't dragged kicking and screaming into the army but joined willingly like most others. He was elected a sergeant in his company.
"soon deserted".....Actually it was the latter part of 1862 after serving several months.
There's a little something they leave out- he also volunteered for a short term (6 months?) in the Confederate army in 1861. That doesn't sound like a Unionist.