Churchill:

“So I thought if we’ve got to do 3D renders every time we see that it’s going to be beyond the budget. Nuke has really matured into a tool that has such good 3D capabilities within a 2D environment – so we went with that approach.”

Mark would sometimes explain how he would do it on an optical printer. That would make the process much more simple[not easier, just easier to problem solve]. There is nothing “not cool” with doing it 2d. The second smartest compositor I know does most techniques 2d. This makes him a very confident artist. You get a lot of information for free from a tracked camera and geometry, but just like a calculator. If you don't know it's wrong who cares that you can do it in 3d.