That's why I said equivalent. The Portable series took the main game, but with different villages and story than in the original (and G), but added tons of new shit. This seems pretty similar, especially when you rewatch the trailer and notice that it actually has most areas from 4 again (not to mention that the core gameplay still looks like the usual MH). However, this time they've clearly put even more new things into it, since G is already out. I just don't think this really looks like a spinoff. The cat game was an actual spinoff, or the RPG.