Have we even seen anything from Ultimate's project plan? I know we have some pages from Smash 4 and I think Brawl..?
Anyway, of all the echoes, Chrom was obviously not planned to be there from the start. His whole inclusion screams "last minute". His character model is ported from Robin's Final Smash, which, speaking of, he's still part of... his facial expressions are kinda weird and his unique animations look kinda rushed. He also had the wrong victory theme at launch lol.
And because she's a lazy inclusion, I've seen people claiming Daisy was a last minute addition but we have hard proof that she's not. The error that caused her turnips to behave differently was a carryover from Smash 4 Peach's data, meaning Daisy was made during a time when Peach was still running on Smash 4 assets.
We do have some, but it's a very hard to find article that wasn't on Source Gaming. I've linked it before, some years ago. It's quite possible the article was lost too. :/ It's pretty rare that Source Gaming is missing an article, heh.
Either way, it just means Chrom was worked on later than some(being he has different animations from Roy overall, that makes sense he took longer). He was still intended to be in from base game, though. I honestly always felt Chrom was one of the last characters developed anyway due to the bugginess, but was going to be there anyway.
Honestly, him being developed last minute wouldn't be that odd. There's always going to be an order of characters worked on. And he doesn't, as I said, match Roy's animations outright. Ken also has this, so they were likely the last two in development or simply the last ones finished of the Echoes. We also had Data of PP's gameplay by September 2018(via a datamine of a demo), so we knew it was worked on a bit after the final characters were mainly developed(if not finished outright. Minor tweaks could've happened all the way till November, when the game went gold). But that said, if they finished Chrom and focused on PP outside of other gameplay, this would explain his bugginess too. They simply didn't do enough and went to other parts.
https://nintendosoup.com/iwata-asked-sakurai-to-make-smash-ultimate-before-his-passing/ At the moment, this is one semi-close statement of it. But it's not the actual details I'm looking for. As I said, hard to find, so apologies. X.X
Actually, here it is, though in an unexpected spot;
Incineroar was the only one not decided upon when the project started. Instead, a space was left for a Gen 7 Pokemon from Pokemon Sun & Moon.
https://sourcegaming.info/2018/12/12/sakurai-tells-more-details-about-smash-ultimates-development/ There was definitely another statement different from this, but it could've also been an odd translation by the website that put stuff in based upon this. PP is a bit more of a mystery, due to also being in the same interview, especially since we know Sakurai isn't exactly keen on "cutting content for DLC" anyway. That, and the amiibo makes PP after all the base game characters too, but regardless, I won't go into that whole thing. Ignoring that one character(PP), yeah, the rest were part of the project plan as quite clearly stated here, even if the oddest spot possible. XD