It’s not a confederate flag.....it’s the Battle Flag of the Army of Norther Virginia.
The flag of the Confederate States of America was the Bonnie Blue.
You’re right, it is the battle flag. The CSA flag was the Stars and Bars, which had a red bar, white bar, and blue bar running horizontally. It caused some confusion on early battlefields because of its similarity to the Stars and Stripes. The Bonnie Blue Flag was an early contender for the official CSA flag.
I have used the Bonnie Blue flag on the bumper of my last couple pickups. Fools don’t know their history.