You still need 6000 gems to get into Gnasty's World. Also, while the skip in that video was done on PAL (higher jumps I believe), I've now managed to pull it off on NTSC too.
With this skip, completing Gnorc Cove is still a requirement as it opens up the Twilight Harbour head which is needed to make the jump into Gnasty Gnorc. Overall it would save near a minute.
Speaking of Gnorc Cove, there's a new skip there too:
Link to video