I remember seeing the saber construction in the ROTJ novelization as a kid thinking it was a cool bit, but in the flow of the film it makes no sense. I can see why it was cut, or more likely why it was newly created.
If this had been in the film you would have the "big moment" of Vader informing his welcoming party the Emperor is coming to check on the Death Star 2 construction. Big fanfare music. Then Vader goes downstairs "Luke... Luke... Join the Dark Side...."
ending the scene on a much weaker note. After all, Vader says almost nothing but "Join the dark side" during the final act, so this is redundant.
Then we see Luke setting a plan in motion that undermines the tension when hologram Luke offers the droids as a gift, now that we have foreknowledge that he built a saber (as presumably gave it to the droids).
I wonder if this is an actual deleted scene or something new to build hype and sell Blu-Rays.
After all, Vader in a hallway that could have been built on a shoestring. I've seen bigger shots done for SW fan films. A possible outtake of him on an elevator, followed by an alternate take of him in his meditation chamber. Wipe to a very cloaked Luke, where we only see a hint of his face. Since we barely see his face and he never changes expression it could be Hamill's face digitally painted over a stand-in. The cave is nothing but shadow. The entrance, exterior, and C3PO could all be a digital composite.
My gut tells me this is more 2010 than 1982.