3D sketch functionality disabled but still sketching in 3D anyways

[FrodoLoggins]

[jeff_strater]

it is important to understand what this option does and does not do.  The description in the options dialog is the more accurate.  This option only controls the behavior of the Line and Spline commands, and whether they snap to model geometry off the sketch plane when they are active.  It also controls the appearance of the 3D sketch coordinate system to allow you to temporarily sketch on other planes.  Also, it only takes effect the next time Line or Spline is started.  If you are in the middle of a command, it will not take effect.

However, it does not force a sketch to be 2D if it is off.  You can still use Move or constraints to cause sketch geometry to no longer be on the sketch plane.

So, we really need to see a screencast of how this sketch was created to know if there is a bug or not.