My other point is this...whether or not it was planned as a port or not is irrelevant. My point is more that the idea may have been proposed, but then changed depending on the desires of the director.
Kimishima is a smart man. With him in charge and having Sakurai get to work on another Smash game, and with Smash Wii U having arguably the most stacked all-star roster in gaming history, I cannot see them not at least going back to the negotiating table for the characters who they acquired, or putting in exceptional effort to retain the roster.
There’s also the fact that the Switch install base is already far larger than that of the Wii U. Like other games, these copies have outsold their Wii U predecessors. While this Smash game may not be a straight up “Deluxe”, I see no problem with the dev team reusing assets, but altering animations, hitboxes, and appearances while also adding characters on top of what was already added.
Given the time between games, State/direction of the company, and dev time, I think it’s entirely possible that this is building on what Wii U left rather than taking bits and pieces away.
I also don’t know that Sakurai would add characters simply to cut them in the next game within 3 years. That just seems weird to me, but that’s me.