It's true that some phone cases that fit the iPhone 12 will fit the iPhone 12 Pro, like the Apple ones. But the PITAKA case has a raised ring to protect the camera. When we put the iPhone 12 MagEZ or Air Case on iPhone 12 Pro, the camera part doesn't fit quite well. Vice versa. So PITAKA makes two cases, with different rings, for either model. The camera dimension is slightly different, which can't be observed with naked eyes.
Other phone cases do not have the same kind of ring design, so they don't need separate cases for those two iPhone models.