I find this a bit confusing because the starting question and thread mix together a number of very different things: single shot vs a tracking mode, focus and recompose, back button vs. shutter button, moving subjects vs. stationary subjects, lighting, and maybe more. The fact that I use Canon may make this even a bit more confusing because the terminology is different.
Nonetheless, i think the only way to get clarity is to separate these things. assuming Nikon works like Canon:
-- the back button, like the front button, is simply binary: on or off. The two cause exactly the same response by the camera.
--at least on Canon cameras, there is no need for a "focus lock" option: when you take your thumb off the back button, AF stops. That is the primary reason I use BBF for 95% of my shooting. I want to control when AF is on and when it's off, and I want that separated from my decision about when to trip the shutter. I do often do use shutter control of AF when I'm tracking something moving--say, a runner in a marathon--because under those circumstances, I don't want to stop AF earlier than tripping the shutter, and it's simply easier to leave AF on the shutter button.
--re the accuracy of continuous vs. one-shot focusing: I have often wondered about that but didn't have an answer. My hunch was that single-shot was more accurate for static subjects, at least if operator behavior is included in the consideration, because on Canons, only single-shot AF provides focus confirmation. This thread has taught me that this hunch was correct.