The real problem here is the misunderstanding of the vernacular. Upside down does not mean turning your head 180 degrees so your skull is pointing at the ground. You're changing your perspective when you do that, which is not what the camera lens is doing. Bruce is correct in that the lens (all lenses) reverse the image in both vertical and horizontal planes.
I'm actually bored enough today to have spent 4 minutes putting together visual aids.
First image is a flower in a vase, as we would see it with just our eyes.
Second image is what would be considered upside down. Notice that there is no side to side reversal.
Third image is what would appear on the ground glass of a view camera.