I tried using back offset but it does not help. Any other solutions you posted won't really help either i am afraid. Sooner or later there always is something that pops up somewhere in reflection, or when it's outside but cast shadow inside of the camera frame.
What i mean is that ultimately, every solution that relies on adding or deleting instances during animated sequence will fail. So i was looking for something that would not remove nor add any instances during entire sequence, but would place instances on surface camera sees during entire time segment, not just in current frame.
Think of it as a limit to visibility feature, but it would not place instances on visible area of only the current frame, but rather entire segment.
I sort of did that already. I created include area spline, and then i moved my timeline each 10 rames, and adjusted the spline to extend forest to the area i see. I did that manually for 1000 frame animation, and it was very tedious process, and it also was not nearly as accurate as forest camera clipping.