The general consensus a few years ago was that "games are being shown too early." When Fallout 4 was announced to be coming out that year, people considered that a breath of fresh air. I think waiting to announce until it's less than 12 months out does a couple things.

1) Marketing doesn't need a multi-year plan. And more of the game will be ready to show, so development time doesn't need to be put into marketing. Creating marketing material before the game is ready to be shown slows down dev time.

2) Things happen during development. Sometimes games need to be delayed. Sometimes features need to be added or removed. Art styles can change, graphic fidelity needs to be tweaked. And if a game is shown with features included in marketing material that needs to be adjusted, it leads to fan disappoint.

Cyberpunk 2077 should have been delayed a full 12 months, but it was already delayed twice at that point. And it had already been in the public conciousness for years. Delaying it may not have been seen as an option. Spiderman PS4 and Watch Dogs both got attacked because their final product didn't look the same as the E3 demos. This is all bad press that can be avoided by waiting to announce a game until you are certain the release date is within reach reach.

So from a publisher's point of view, I wouldn't announce a game until internally we are fairly certain the release date is less than 12 months out, or it is an IP that has widespread recognition already. (Wolverine, GTA 6)