Perhaps all of this comes back to the hacking. If one ignores Paalm, then Trellium may only be allomantically/feruchemically/hemalurgically viable via hacking. Wait. Just remembered something. If Paalm needed a steel spike, for example, to steal Idishway(?)s Feruchemical speed, then didn't she have two spikes? One of steel or whatever else she was using, and one of Trellium? If so, that could explain the lack of glowing red eyes. Maybe it didn't count as hacking enough for that.