Think you are right (didn't even see it before), but the resizing possbility was very limited in 6, to the maximum size of the Properties panel only. When you make panels floating, some can still have their width being increased like the Library (which I often make floating). As I answered in many threads, the only way to increase width of the Properties panel is to drag it to the bottom dock, where the Timeline is sitting.
I have already logged multiple feature requests to allow more customisation for panel size, to turn the Advanced Actions dialog box into a real panel, with full customisation possible etc. You can only add your voice by entering also a feature request.
You cannot resize this panel beyond its maximum width. My workaround is to
drag that panel to the bottom dock, it will adapt to its width. And this was also the same answer I already posted. Why didn't you try it, it was in the same thread?