Does it really become moot with a full volume boil? Looking at hop utilization vs gravity, there could still be benefits in waiting to add a portion of extract until the end of the boil in order to more fully utilize hops. Don't know this from experience at all, but it would seem that if you're doing a high gravity, highly hopped beer you could take advantage of that. But then maybe I'm way off base. My knowledge is still mostly book knowledge, with only three real brews under my belt so far.
The point I was addressing was that not doing a full volume boil will mess up your hop calculations. That is, if your recipe uses a hop schedule that results in, say, 40 IBU but you only do a partial boil, your IBUs won't end up at 40. Likewise, if you do a full boil with late extract addition, your IBUs still won't end up at 40 (probably off in the other direction but off nonetheless).
If you're just trying to maximize hop utilization then yes, the extract late full volume boil could increase it. Although I'm sure there are gravity and utilization limitations that'll come into play at some point.
Oh, it looks like you're new to the forum, WELCOME!