Tree 'Fade Length' Not Working as Expected...

I am NOT noticing any difference in changes to the ‘Fade Length’ or ‘Billboard Start’ settings on the way trees transition from 2D to 3D. That is, I expect to see the trees transition (geometric morph) from 2D billboard to 3D smoothly over the set distances.

For Example: With a ‘Billboard Start’ of 100 and a ‘Fade Length’ of 50 I expect to see everything from 0 to 50 (relative to the camera) as a full 3D tree, everything from 50 to 100 at some point in the transition from 3D to 2D, and everything from 100 to the ‘Tree Distance’ as 2D. Instead I see the trees instantly POP from 2D to 3D at the set range and adjusting the above settings only seems to moves the distance at which the popping occurs.

Am I missing something? Does this only work with specific trees model types (Speed Trees) and/or render paths? Or is this just another bug, from as far back as version 3, that has yet to be corrected?

Unity terrain system is indeed from as far as version 3 and not much has changed since then. Even with Speed Trees, fade length does not do much, since they have got their own options for fading.