It's just a clip from his stream earlier today with a few bits from older streams mixed in, in which he discusses his level and how its deletion is an example of a bad policy that he has a unique platform to advocate about. Could it a bigger, more comprehensive video? Sure, but he says there that he doesn't need to do that because places like Polygon, Kotaku, Waypoint etc. will cover it and do a better job of speaking to it than he could anyway.
He's referring to Nintendo as a singular entity because they are in terms of moderation. Any employee moderating and representing the company is professionally speaking for them. He's in a unique position because he's spoken to Nintendo employees outside of normal channels about that particular matter and got that answer, most people could not get that answer and would be left with nothing, simply an email that their decision is the end of the matter and there is no appeal.
I've got almost 100 hours in Mario Maker 2 so far and it is the biggest disappointment I think I've ever had in games, despite loving so much of it and enjoying so much of it. The game fails to improve on almost anything from the first game and introduces all kinds of problems that did not previously exist. If you haven't seen negative impressions of it you haven't been paying attention to the hardcore community which has been stymied at every point, whether it's nerfs to kaizo mechanics, removal of music mechanics, issues with discover-ability, online lag, the changes to endless, and countless other issues. That's not to say that people aren't happy to be playing Mario Maker again, but the game has a lot of issues and isn't the sequel that many fans wanted