At least Kirby's in both games!
Everyone makes mistakes. I know I make them all the time, and now we know the people at Nintendo do as well. We’re all human, after all!
An official Switch booklet put out by Nintendo in Hong Kong gives people a chance to look at the recently-released and upcoming Switch titles Nintendo has, and included in the mix is Kirby and the Forgotten Land. You can check out the page in question above.
As you probably spotted, Nintendo accidentally used screens from Smash Bros. Ultimate in the listing for Kirby and the Forgotten Land. They’re not all from Smash Bros., but at least two of them were somehow given the go-ahead. Whoever was checking these pages over didn’t do their finest work!