I feel like people aren't seeing exactly what this trailer likely is. For the last two months, we have been getting teasers of a new pokemon and then within the week or the week after, they reveal a new pokemon. They have done this for two months and they did it with Hisuian Zorua and Zoroark.
They set this trailer up to be exactly like that, but in a different form of a Vtuber given us hints and fact about a new pokemon. She says guess before my next stream which likely means Friday or sometime next week.
The only mistake there was is the fact that they announced it a day before. If there hadn't been a single announcement, I don't think people would have mind and would expect the reveal at a later date.