Thinking a bit more about it, and considering how no other Nintendo social media channel has acknowledged the new Tetris 99 Maximus Cup (nothing on other branches' YouTube channel, nothing on Twitter at all), I believe there's a strong possibility the YouTube upload was mistakenly scheduled 12 hours early. IMHO it was going to be posted at 18:00 PST / 21:00 EST / 03:00 CEST / 10:00 JST, which is the typical announcement time for this kind of updates. I'll try to go a bit more in detail later though, since the announcement day may still be a hint. Maybe.