You'd have to completely ignore the one story reason for infernal iron being in the game in order to look at enriched infernal iron and say yea that's just a paper weight. It doesnt make any sense to add in something so specific if infernal iron would work just fine in its place unless it was intended to have a different effect. The only effect it could have is as a fix for karlachs engine or as you suggest it's a pointless paper weight. As far as larian not speaking on it that's just wishful thinking tbh. If you want to poke holes in everything that's fine but at the end of the day I don't really care. Karlach needs a better ending than the ones she has now given how needlessly depressing they are.
That's not wishful thinking that's fact. Larian never teases or announces anything, unless it's ready to be shipped so there is no way and no reason they'd do exception for Karlach. And since they're still patching the game, there is no reason for them to say they are finished with anything. As for enriched iron, there is like million possibilities it could be used in some quests in the Upper City, no reason to assume it was tied to Karlach's cure that might never been planned in the first place (and likely wasn't, at least not until very very late development)
