User blog comment:BannedLagiacrus/Monster Appreciation Week: Rathian (5th Gen)/@comment-4969421-20180325174000/@comment-3298463-20180325194749

Apart from the barely-changed moveset, there's another thing that I think supports the idea of Rathian being kind of "forgotten" or put in the backburner: other than Bazelgeuse and Kirin, she is the only non-subspecies monster that's introduced in an optional quest and has no intro cutscene.