Yes, the default behavior for CGC Core Engine is the StS format you have outlined if you turn off Deck Editor. If you would like to keep Deck Editor but restrict the number of Decks, you can do so by removing the Command Options Equip, New, Copy and Delete. That way you can still use the Editor interface but disallow players from making more than one Deck. We will have an option to skip the Deck Selector scene and go directly to the Deck Edit Scene in a future update of Deck Editor.