Yes, it is by design that the Scroll bar is inactive.
The reason you cannot see all the fields via the scroll bar is that you cannot change the properties of the Default User Groups; you must create your own User Groups based on whichever group you would like your custom group to resemble. The TDAdmin group is the group with all the permissions, but you may want a custom group that closely resembles the Developer group or the Viewer group.
Please review Chapter 15 of the Administrator Guide for further explanations.

GoDawgs,

The recommendations from HP are: 1) to only have users be a member of one group (to insure permissions are applied appropriately and not incorrectly cross assigned as can and does sometimes happen when a user is the member of more than one group) and 2) to always create a custom user group off of the default TDADMIN group only and remove permissions to obtain the desired users permissions.

(**Note: Creating a custom group off of any other group has been proven that it can create issues with the association of permissions, as for some reason adding permissions to lower groups and creating from groups other than the default TDADMIN group doesn't always yield the desired results. In theory it makes little difference but in practice it can and has in real world usage caused undesired results for the newly created group which can be near impossible to troubleshoot the root cause).

Hope this helps,
Dan