That's pretty normal. Monster Hunter is Capcom's most profitable series ever and they regularly use the skeleton+animations of older monsters for new ones. (did you know that both Nergigante and Magnamalo reuse many of Gore Magala's animations?) In any sort of art related industry it's just smart to re-use assets. I work in the comic industry and it's extremely common to just copy/paste panels or backgrounds because there's no reason to redraw certain things.