Include switch layer interpolation in smart bone action

[TheGreenBrony]

I set up a smart bone action to switch between sub-layers inside a switch layer. The "Interpolate sub-layers" option is checked and, while I'm editing the action, the interpolation looks perfect. (As a point of clarification, I edit the smart bone action over several frames.) However, once I go back to the main line, the switch occurs when I turn the bone, but without the interpolation. Can anyone explain why this happens and possible solutions/work-arounds?

[synthsin75]

Switch interpolation does not work with smart bones.