Okay so I already talked about my counter theory for Box Theory and something that stuck out even in my theory is that the left side would have a conspicuous blank spot if Ken wasn't there which is probably the biggest counter to my counter theory. However upon looking at the box again I considered a possibility that could explain why the bottom row on the left side that contains 8 characters (54-61) and it doesn't involve Ken but first let me reiterate my counter theory.
The Box isn't meant to show the full roster and the box we see is what we're going to be getting at launch and will feature none of the fighters past the 8/8 Smash Direct.
Evidence 1: The box doesn't feature Isabelle
Well of course it was to prevent leaks from retailers. Well if that's the case why did the box appear after Isabelle was unveiled and still not feature her there? The box even appeared after she was unveiled so that counter argument doesn't hold that much water either. It's just weird that we're making assumptions that the box will show off the entire roster when already it doesn't.
Evidence 2: Other forms of marketing also doesn't feature Isabelle
Not the European Special Edition
Nor the banner used in the tailgate tour being done to promote the game.
Which again super odd and in the case of the European edition might imply that's the final box art and doesn't need to feature the characters after the Smash Direct. It also leads the question of why they're showing the box art for the special editions this early? All we need to know are the contents right now and they can show the final box art later. Unless if once again is only featuring the roster as of the Smash Direct.
Evidence 3: No Fire Emblem Warriors doesn't compare to this.
So a common argument used in favor of the Box Theory is that we have cases like Fire Emblem Warriors that showed off hidden characters on their special edition box art before the game came out. However in FE Warriors' case the Box Art was shown off a couple of weeks before the game came out in Japan. So it would make sense that the final box art would've been put out there. In comparison Smash Ultimate is still months before release so why they felt compelled to show updated box art is strange unless if that box art was final and the box doesn't represent the final roster.
So in conclusion maybe Nintendo figured it would be better for all of the external marketing to only show off the roster after the Smash Direct as they wouldn't need to worry about leaks and coordinating making new banners. Just because Sakurai said he would show off all the characters before release doesn't mean the marketing and box arts need to feature them and the roster would still look impressive and eye catching to most casual players just checking the game out.
Now once again the big counter argument for this theory is the left side features a missing blank spot and the spot lines up with us getting a Ken Echo Fighters. Well what if the box wasn't blank and it wasn't Ken. What if the final 8 row fills it up by itself because there was another character that took the slot?
What if it was Pokemon Trainer that took up 2 spaces by itself?
Pokemon Trainer is already a super unique character and the virtue of the character would mean that Squirtle, Ivysaur, and Charizard should also share the slot with Pokemon Trainer. But the way that the slots and spaces are set up makes it seem a bit too cramped to fit the format of the slots. So what if Pokemon Trainer's slot was bigger than usual potentially occupying 2 slot because it would need to feature 4 characters? The Mii Fighters slot already looks super cramped with 3 so maybe this would be a way to accommodate PT.
So the blank slot on the left is potentially Pokemon Trainer occupying 2 slots and the Box is not showing us the full roster and is instead only representative of the roster as of the Smash Direct. Which would explain why the final row has 8 characters just like the current set up only having 7 characters for the right side. Either implying it's the final one or the box isn't final and it could be edited to feature a better design for all the fighters.