Yes; you are right. This is the same problem. I tried to download the latest version of gantry (the 5.2.15), but the problem remains unchanged.
I tested the three different Dropdown Styles: Default, Simple and Extended. The Dropdown Direction to Expand Left, works only with the "Simple" Dropdown Style setup. But, with this setting, you cannot bring in two columns the menu items. The other two setups (Default and Extended) no works.
The solution that I've read on the thread that you have linked me (This is now implemented for Extended menus who define a fixed size
), does not work. In my mainmenu items, the "Dropdown Width" is fixed/defined, yet do not work to the Left Dropdown Direction.