Samsung will have very little control over this in the long run. The companies who write those apps will need to support the nowbar, which obviously is not going to happen on unreleased beta software.
The unfortunately reality is that the nowbar will probably never see widespread support from third party applications, given the fragmented state of Android Apps.
I think you're right, though I think samsung can do it if they've control over Apps notifications, that means they can turn the notification design to now bar when the phone is locked.
