Viewport difference between "entitie viewport" and "single tile" in paperspace.

Hello,
When i make a viewport with a single tile and "display locked" is off i can set custom scale manualy.
Making a viewport by selecting an entitie and "display locked" is off i can NOT set custom scale manualy.

Why is there a difference between these 2 types of viewports???
I work with Draftsight 2018 SP0.

Best regards, Arno