This must be seen in the context of the new Layout:
Here, the tabs are at the very bottom of the main window. When right-clicking on these tabs, the focus is automatically on one of the following:
Close all tabs
Close other tabs
This means that one of these commands gets triggered if you don't navigate to one of the commands (or your mouse focus is out of the menu). Simply imagine you have clicked on the wrong tab – zas, all other tabs are closed. Stupid, isn't it? As I worked last week with Windows only and it did not happen, this seems to happen primarily on Mac.
Anyway, it is not the best idea to put the primary focus on the commands above when right-clicking, no matter where the tabs are located.
> Simply imagine you have clicked on the wrong tab...
Well, simply don't click if you don't wish to activate any of the menu commands. Anyway, the pop-up menu is moved 2 pixels away from the mouse in the latest build.