I'm running on Windows...
32-&-64-bit Chrome
Dev-Chrome
Beta-Chrome
Session-Buddy saves a complete set of all open windows and tabs when I close any Chrome version from the Taskbar. This means using the mouse to [Right-Click] the Chrome icon and choosing from the "Close Windows" context menu.
If I close Chrome from using the [X], the close button, in windows' upper right-hand corner, the session(s) will not be saved.
I believe this behavior is a feature not a bug. Saving sessions using the Taskbar works even when multiple versions of Chrome are active.
It could be useful to have an option to intercept all closings and save sessions with a confirmation dialog window. My own opinion is this behavior would quickly become tiresome and I'd turn it off.