She's holding her normal, right-handed gibson les paulupside-down, and plays it left-handed. That's not an error, but the very essence of the picture. I think artistic error tag was maybe a joke? Anyway I removed it
It's not "flipped", Bocchi is holding her right-handed gibson les paul upside-down, and she is playing it left-handedly. (Observe the guitar, and her hair-thingy.) Unless there is a left handed gibson les paul, and a left hair thingy bocchi, that this image references.
That's not an error, but the picture you're looking at.