DT does not need to be a possibility. Take the following for example:
Match to 4 points - White 0, Black 2
| White | 3 | ||
|---|---|---|---|
                | |||
| Black | 6 | ||
| Position ID: EgAAOAAAAAAAAA Match ID: MAGAAAAAEAAA | |||
• White doubles
White has a correct double while an underdog and outside the market window. If White does not double and does not roll a double, correct cube action is double, pass.
These situations arise when your opponent has next turn an efficient in-cube, an efficient out-cube, or a cube that snuffs out significant remaining winning chances.
To illustrate the latter point:
Match to 4 points - White 0, Black 2
| White | 6 | ||
|---|---|---|---|
    | |||
| Black | 4 | ||
| Position ID: BgAAYAAAAAAAAA Match ID: MAGFAAAAEAAE | |||
• White doubles
If White fails to double and fails to roll a double, Black's double out is not particularly efficient (a 0.4 error to take), yet the diagrammed position is a double outside of the window.