The point of that image isn't at all "who's making it".It's completely possible they still are (re)negotiating the deals with 3rd parties. Metroid Prime 4 also is "©2018 Nintendo" even if it is being done by an external studio that should be credited too. I'm also not sure how the copyright situation works if the name is probably getting changed.
It's comparing the dates that are shown on the copyright for known re-releases with the date for SSB. The re-releases show the original year to 2018. Smash just shows 2018, like new releases do.
...Everyone.
Not everyone but a lot of people.
I also believe it to be a new title but BotW Link isn't proof of that as that could be an added costume.