That's definitely very odd, and definitely does not look like typical Superia. There are proper black and white tones in these two images, but some tones in between look very strange. An overexposure by two stops should have been handled without any issues.
As you probably know, these scans you got are most likely not straight scans, or just inverted to get positive images. These scanners try to apply all kinds of corrections to get you contrasty and colorful images, and sometimes these auto corrections get it very wrong. If you are familiar with image editing software, you can probably correct these images, otherwise you'd have to contact the lab to get these scans redone.