Browser 'Back' button (Sugarcube 2.11.0)

Can someone please clear up a little puzzle. When I test my game in the browser, the 'Back' button remains inactive throughout. When I discovered this I was delighted, and assumed it was part of Sugarcube's make-up to stop people casually pressing 'Back' when they made a bad or fatal choice in the game. But on testing several other games from Twine's main page - some of which clearly use a version of Sugarcube - they all have an active browser 'Back' button when playing, and as feared I can simply hit this to return to the previous passage.

Is the inactive browser navigation unique to Sugarcube 2, or am I missing something here?

My browser is Firefox and please note I'm referring to the browser's < > buttons, not Sugarcube's 'Backwards' / 'Forwards' links.