An important thing for the plausible deduction of drops "in this genre".
Let's take an example, why do NF Dryder drop skins that you can also have on these monsters and available only in the Underworld? (Ghostly, Eternal) And also why do Titan drop Magmas also in NF? But above all, why, in most cases, do monsters that are "recycled" in this way for a quest or another campaign not drop the skins that were originally dropped?
When creating the instance concerned (development), monsters are linked to certain skins. Those that are specific to them and those that are linked to the region and campaign concerned. In some cases, however, this has not been coded correctly, or, to put it another way, has not been updated properly.
For example, the Hallowen quest in 2010: Commandeering a Mortal Vessel, saw bugs on weapons. Idem for NF's Dryder and Titan saw Prophecies' original weapons made available to NF in inscr. version.
If you're looking for other skins with this potential bug, you shouldn't be looking for monsters directly linked to this skins (e.g. demons), but for those that "bug". Just find the skin, even in blue, to confirm it (not only gold in this case, as far as inscr. versions are concerned as opposed to their no inscr. versions), it's not that difficult. Insisting on 10,000 monsters and averaging them out is pointless.