He never mentioned Nicrosil, only Aluminum, though it seems likely that at the time of this quote he already had in mind some of the tricks that he revealed in Bands of Mourning. However, in the very same quote he points out that the MAG specifically does NOT explain everything the metals can do.FROM BRANDON
None of the Enhancement Metals are well understood during the days of the Final Empire, in part because they’re so hard to come by. This and subsequent metal chapters, and the rules within, are presented so you can have fun and experiment, rather than as a complete explanation of everything they can do. To reveal them in full would ruin surprises intended for much later in the series.
That said, however, consider the implications of Aluminum in Feruchemy. With proper manipulation, it might be theoretically possible to tap someone else’s metalminds...
Elsewhere he has also said that the MAG metals are not considered canon. He gave Crafty what information he felt appropriate at the time and then let them speculate as to what the powers could do, and specifically did not make any corrections that would spoil secrets for later books. It's pretty clear that Bands of Mourning was one of those books. Also, Crafty themselves [urlhttps://www.reddit.com/r/IAmA/comments/4soujz/i ... nd/d5b0oqo]have indicated that they will be addressing and correcting the metallic powers revealed in the most recent books[/url].
So anyway, long story short, the rules for Nicrosil in the MAG are a fun and interesting idea for how Nicrosil might have worked. I've played campaigns that use those rules and they've been enjoyable. For this campaign, I'd like to use the alternate rules for Nicrosil that we came up with that more closely align with what we see in the novels. I think that they will be equally fun and interesting, just in different ways. I hope that's alright with everyone.
EDIT: Do note that on many levels our homebrew Nicrosil rules accomplish the same things as the MAG rules, just in different ways. MAG-Nicrosil lets you tap nicrosil in conjunction with another metal to get more power out of the other metal. It does this by adding your Nicrosil charges to the tapped charges of the other metal.
Homebrew-Nicrosil lets you get more power out of other metals by making you a more powerful feruchemist in that metal. This means that you can tap greater chunks of charges, reaching some of the higher echelons listed in the "Tapping 10+ charges" sections. You can still also tap nicrosil in large chunks to add nudges and/or increase outcome when used in conjunction with other powers.
In the end, both versions increase your power in other metals. Homebrew Nicrosil has the potential to increase your power to far greater levels than MAG-Nicrosil does, but does so at the cost of tapping more charges of that metal.