I would think that the actual movie is public domain, and the "restore" copyright only covers the new work done to the film.
Face it, Copyright laws were pretty much turned upside down thanks to Sonny Bono and Bill Clinton.
The intent of the Bono act isn't to restore copyrights on things that already entered PD. But Golan v. Gonzales somehow establishes that copyrights
can be restored under specific circumstances. The movie was released in 1927 (or created in 1924, whatever date works for you) which places it within the Bono act.
How that affects those $1 Big Lots movies beats me. I suppose the owner can demand those discs stop being published then probably deem the profits from a few thousand $1 sales (incomplete to boot) isn't worth the effort.

I was just at Big Lots a couple of weeks ago and I don't recall seeing Metropolis on the shelves. Maybe they've already sold off whatever existing stock they had or they were pulled.
Moving along, this film is
gold. I watched about 15 minutes of the film from PBJ's link on the big TV this morning and it easily hooked the seven year old. I can't even get her interested in any of the modern Japanese flicks I have, but an 80+ year old film seems to enthrall her.

I really want to get a copy of the full film.
The only thing I can't seem to get over is the weird uneven lighting these old movies have. It's like looking through a peephole most of the time.