They never claimed a timeframe for the announcement, just that these would be the DLC. Seeing literally just a development build of the game would have shown them most of what they claimed, since there's a giant button in the menu with DLC key art in it, now, which explains the uniforms if you dig into it. It's not clear how they would have known about the new paradoxes, though those aren't exactly the most well hidden (their moves have even been showing up in what I understand to be official TO tools as well as datamining) and the purported detail that Ogerpon has a unique Terastall appearance (a detail which remains unconfirmed). Also, like, anything involving 1.2.0 would have been done for some time now, so it would be pretty obvious what was included if they were involved.Ehhhh.
My biggest issue is that it seems like way too much information for a single outsourced programmer to know. Like, I'm trying to picture what exactly is your assignment that you'd know, say, the names of DLC; that there's new outfits, let alone in 1.2.0 specifically; know that there's a turtle Pokemon and they're the headliner for a DLC; know that Paradox Suicine/Virizion are imminent etc. Even their assignment was a general "make these DLC areas look not janky from start to finish," such that they were aware of all this information, how did they know, say, Topopogos would be shown today and not saved for a later announcement? The only job I feel that naturally brings you in contact with all this information exactly is the PR department or someone who had access to the Presents' materials proper--which contradicts their assertion that they're a programmer (and in turn suggests they are not working on the graphical patch that makes this discussion interesting).
Just something about it feels sketch. Idk.
I'm not saying that you should necessarily believe this, because the proximity to the stream is a bit of a red flag, but a lot of what they said is information that would probably be difficult to really hide from someone with access to dev builds of the game.