Sorry for the misunderstanding. Yes, I said there were tinges. I didn't say Skyfire were metalcore.
Anyway, to restate my reasons; the vocals sound closer to Trivium than any metal I've heard. The chugging riffing at the start of Bereaved in Denial is rather core-ish, it certainly doesn't sound like any metal I've heard. The syncopation with emphasis on the first beat in a lot of the riffs is used a lot in core music, not so much in metal.
Again, there's a slight influence - I would have thought that undeniable. That means I think it's not 100% metal, no big deal. It's not an insult to the band or anything, unless you don't like core music.