It is, but I feel like the presentation of the game might have obfuscated things a bit. Its an SMT styled game with FE themed characters, rather than SMT characters meeting FE characters, which would be the more blatant gimmick. It certainly doesn't seem like it was massively stocked either - less than 60k copies if I'm doing the maths right (apologies, kinda new to this).
Still, Wii U hardware numbers are pretty damn good (relatively speaking), and Splatoon and Super Mario Maker are still selling a tonne, so I doubt Nintendo will be too upset. Should be interesting what (if any) sales they'll be able to retain after the holiday is gone.