Since you've apparently missed it, here it is again....
Thanks for sharing this again! I actually did see this though. I don't mind addressing it specifically.
First, he points out that Sakurai's tweet says, "Ultimate's DLC lineup is now complete", and argues that this really means the DLC lineup has only just been finalized. I think this is stretching quite a bit. The reason Sakurai told us that the lineup is now complete was to make it clear that there is no point to begging for certain characters, because it is already decided. It does not necessarily mean that the lineup was only just finalized. It is compatible with his tweet to suppose that the lineup has been finalized for weeks or even months. Even if Sakurai grabbed his English translator and made him write those tweets the very instant that the lineup became final, that would mean that Matt Bozon was making his Shantae for Smash DLC tweets while negotiations were still ongoing. I doubt he would do that.
His second point is that Nintendo choosing the characters doesn't mean there won't be third parties. That is true.
Finally, he reads Sakurai's tweet as suggesting that Nintendo gave him a decent list of characters to choose five from, and Sakurai had creative freedom within that list. Really, we don't know either way, but I didn't interpret Sakurai's tweet that way at all. The way I read it, it sounded more like Nintendo told him which five characters they want, and unless Sakurai could give them a compelling reason why those characters wouldn't work for Smash, it wasn't up for negotiation. Considering Sakurai could make basically anything work as a Smash Bros character, it would have been hard for him to argue that any of Nintendo's requests were impossible to fill.
As is always the case with this sort of thing, nothing is certain. There is still a real possibility that Shantae is among the DLC characters. As I explained, the main thing about the tweet that makes me less than hopeful is really the timing. I just don't think Matt would have been making tweets like that if WayForward and Nintendo were even discussing the possibility of Shantae DLC.
Based on my reading though, things aren't looking so good.
EDIT: Here is the tweet I am addressing, since the link isn't captured in the quoted reply above:
https://twitter.com/Unit__NineS/status/1060013828744900608?s=09
You really think Sakurai is trying to play the blame game with Nintendo?
Honestly yes, if you want to put it that way. More accurately, it seems like Sakurai is trying to publicly wash his hands of responsibility. Frankly I found it very surprising that he actually came out and said, "Nintendo chose the characters, not me". Isn't it a little unusual that he would specify who chose the characters? That isn't even related to the main point of his tweet, which was just that the characters are already selected so there's no point in asking about it anymore. As I said, I get the decided impression that Sakurai does not think the DLC characters are going to be what fans are hoping for, and being rather sensitive to fan feedback, he wanted to make it as clear as he could within his professional obligations that these were not the choices he would have made.