There are numerous different strains of brown trout, and quite a few different strains of brook trout as well.
Just speaking from here in Maine, there are 3 different strains that are stocked out in ponds, plus our naturalized strain.
There are at least as many strains of brookies too, all have some different characteristics.
Genetics are a funny thing, so a tiger trout that comes from a Male Brookie x Female Brown may not look the same as a tiger that comes from a Female Brookie x Male Brown.
All that aside - yes, its a tiger.