My guess is that they had the idea of the Gondians and the Steel Watch, but made it part of the infernal engine questline when they came up with it. Because if you take out the knowledge of infernal machinery, the Steel Watch and Gondians concept still works. And the refined infernal iron used is just to show the difference between the level of tech. Which might also explain why we get a single bit of dialogue with her explaining they cannot fix the engine according to the Steel Watch.
It is certainly disappointing that's how it is. Because as we've been saying for... 140 pages, this could have been done to finish her story in a happier fashion. One that felt more complete but we ended up chasing red herrings that were not intended to be inferred that way. After all, it's easy to assume players will take something one way when you've designed it as Larian did/what I said above. But without that context of adding the infernal engine later when the Gondian quest is made, it's incredibly easy to assume the refined infernal iron was part of cut content, there was intent behind it, etc.
Ultimately, with the epilogue party, I'm content with the story as is now. My biggest issues were much the same as others had, where it doesn't feel like we actually have an impact of helping our companion like we do with others. Certainly was still emotional and well written in the bubble, but it felt very poorly done when everything was brought together. With the epilogue suggesting the engine design in avernus and the forge, it feels like our actions, and our support to go to Avernus rather than die, that we're able to keep her story going and open ended, which is really all I needed from the story, rather than a forced tragedy.
I'm still not completely satisfied because it DOES feel like we try all of 0 ideas in act 3 to fix it ourselves, but I am satisfied that they are trying to remedy that with what is offered in the epilogue. Who knows maybe they will make a DLC after all to stop a new evil high level plot, and include fixing the engine along the way to make it really feel whole.
