I don't know what you mean by "pre-post indicator flag"... so I think the answer is no but If you can clarify, maybe this is something that can be added.
Take a clip and adjust it's size using Pan/Crop. Now add any effect (the Border effect in my case). At the bottom of the Border screen is the timeline with keyframes. To the left of that is the control name and on the far left is the Pre/Post triangle (i.e. does it happen before or after the resizing). I need to toggle that flag from my script.
Ah... OK... yet another feature I was not aware of.
But now that I know, I've added the ability to get and set this flag via script. However, I can't promise the change will make it into the 4.0d release. There are some difficulties that may arise given that this switch causes the effects collection to be resorted... further measures may be needed.