What went wrong?

With both Smooth Quartz and nether gold ore/quartz both being vanilla blocks, it makes no sense that the id would be "excavated_variants:create_smooth_basalt_nether_gold_ore" for example.

This, of course, also would have the Create mod installed

Platform

Forge

Version

1.18.2-0.6.4

Logs and Screenshots

the nether variants have "create" while the diamond one below does not

Nether smooth basalt and overworld smooth basalt are different variants. This is intentional.

Regardless of Create generating smooth basalt in the nether, both the blocks used to generate the ore are vanilla

Yes; that's irrelevant. The stone object created by Excavated Variants is only present if create it. Vanilla and create smooth stone ore variants use different stone objects