Both Nether Gold and Gilded Blackstone aren't in /smelt yet. @Unique_Beagle said it's prob an oversight, thus why I posted here. Edit: prob all smeltable 1.16 blocks as well aren't in the /smelt table. but I haven't checked yet.
Nether gold has been added and will go live soon. Gilded blackstone is not smeltable and thus won't be added.