Because since 6.0, WinSCP can work as a local file manager (with two local panels):
Issue 1893 – Local file manager mode (two local panels)
So while before a session and a tab was basically the same thing, now you can have a tab without a session. And most commands in that menu with a tab (with or without a session) not with a session.
Issue 1893 – Local file manager mode (two local panels)
So while before a session and a tab was basically the same thing, now you can have a tab without a session. And most commands in that menu with a tab (with or without a session) not with a session.