windows 10 local admins group.

Our end user computing team seem to have created a custom group that is a member of the local admins group on all* Windows 10 devices. I need to verify membership for an appropriateness check but wanted an understanding how that would typically be rolled out to all windows 10 devices, i.e. if you created a new AD group with members, and then wanted that group to be attached to the local admins group on all Windows 10 devices, how technically would you do that? And secondly to that, is there any chance it may not be 'rolled out' to all Windows 10 devices, and how easy would that be to mess up, or what kind of issues/mistakes/exemptions could prevent that intended all device change taking place/