Undocking plugins by dragging the tab: not working properly

In X1, I could drag a tab from the unfloating multidock and the respective plugin would undock and be displayed shrink-wrapped to the size of the plugin's interface.
In X2a, when I drag a tab from the multidock, the respective plugin undocks but is displayed as wide as the multidock area and as deep as the title bar only (10mm?) so I have to manually resize it up and across to make it usable.
To get the results I enjoyed in X1 in X2a, I have to right-click the tab and select Undock - this undocks the plugin at full shrink-wrapped size.
Anyone else get this? Have I missed something... ?