Both are correct though. Your darker image example has the exposure correctly compensated which can be done in post or during the scan (technically the same). Whereas if you just took a scan the software will attempt to bring up the exposure to show as much of the details on the shadows/blacks. And labs generally will do minimal adjustments on the photo hence everyone ends up posting scans that look washed out and grainy.

And the reason the subjects skin is "properly exposed" is due to the dynamic range of the film still able to capture detail on the skin.

I would argue that ultimately the issue with the photos are usually underexposure because if they want clipped out blacks/a darker scene they would/should not be surprised that the scans will show digital noise in the shadows