This. I could write an essay on why spirits do deconfirm no matter how much you want to believe they don't. Every argument for why they don't has a good counterargument, like...
Trophies didn't have a role in battle. Spirits do, since you equip them (and they represent the souls of those who were killed by Galeem and never got a chance to come back). Also, Mewtwo and Lucas were veterans, which seems to be the exception to the deconfirmation rule, since Samus, DK and Toon Link still made it in to Ultimate, Brawl and Smash 4, despite having a non-fighter role. No newcomer ever did that besides Chrom (who was last minute and I explain why we know that after the next quote).
And all of those characters that can be equipped by themselves are either alternate versions or actually something else. Tree isn't Wii Fit Trainer. It's a manifestation of the pose. Plessie isn't Mario, but only shows him because there were no preexisting renders of Plessie. Kaptain K. Rool and Yarn Yoshi are treated separately. It's like how Dr. Mario and Young Link are treated separately from Mario and Link. Only difference is Dr. Mario and Young Link got in while Kaptain K. Rool and Yarn Yoshi got deconfirmed.
Chrom is a last-minute addition, as shown by how he only got the Awakening Victory theme in the 3.0 Update. Before then, he has the standard FE Victory Theme. If they didn't even get to change the victory theme in time for launch, they wouldn't have time to Change Robin's Final Smash to something that didn't have Chrom.