I hope you mean that you can use groupboxes in resizeable dialogs as long as you keep the groupbox stationary, ie not resizing them at all, to avoid flicker,
You can use groupboxes in resizable dialogs. But, in the current implementation, there is some flicker. You can see it in the augmentedResize.rex example. When you size the dialog, you can see the text of the groupbox flicker. The alternative, will not draw the controls inside of the group box correctly. And is very, very much worse.
So, for the augmentedResize.rex dialog, you would have to decide. If the group box flicker is acceptable, then you can use the groupbox. If it is not acceptable, then you would need to design the dialog without a group box.
the same for static Controls.
From what I've seen, if the static control remains fixed in size, then the current implementation words fine. But, if you have a static control like the one in Staffan's test, the text is not drawn in the correct spot, and looks bad. If I handle the static control the same way as the group box, then that problem goes away. But, the flicker goes up.
What I'm proposing is to allow the programmer to specify if the static control should be handled like the group box, or not. That way, if your dialog has static controls and seems fine to you, then you would leave things alone. If Staffan's dialog look bad with the text painted in the wrong place, he could turn on static handling is the same as group box handling. Maybe an attribute in the ResizingAdmin:
treatStaticLikeGroupBox = .true