If you can get a line in the tree and have enough pulling power to get control of the tree there is, in my opinion, no reason to back cut first. The line will keep the tree from setting back.
If you don't have enough pulling force or leverage on the tree to keep the tree from setting back, you don't have enough leverage to pull the tree over then either. If the tree is leaning that heavy or is that big then it's probably not a candidate for being wedged over either.
IMO back cut first is a valid technique but is only necessary in very specific situations. It has to be a tree of a very certain size. A tree that is very wide on the stump you should be able to cut a face and enough back cut in to set a wedge before the tree starts to set back. Given the size of tree that lends itself perfectly to back cut first technique if you are able to get a line in it and pull, there's no reason to back cut first.
Also, in my opinion, back cut first is not a technique for someone that needs to ask on an internet forum if it's a good idea. This is an advanced technique and should not be attempted by beginners or if something valuable is within the fall radius of the tree. Now, if the tree is in the middle of nowhere and you just want to give it a shot with a line in the tree as a back up. Go for it. Cutting trees is fun and trying new things is a great way to learn. Just be careful and have someone there with you.