The point of the embargo isn’t to be helpful to a player, nor is it a defensive measure caused by lack of faith in the quality of a product. The point of review embargoes is to concentrate all of the news to drop at once in order to maximize the interest in the game at that point in time - usually right before the game launches. This encourages discussion and comparison around the game in the crucial days leading up to launch. If there were no review embargo, reviews would trickle out over a period of weeks before the launch, dulling their impact.
That’s really all there is to it - the marketing department wants to maximize the interest and talk about the game right before it comes out, so the review embargo is in place to ensure that happens.
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