Of course it does. And why not allow the reviews to be released directly after the keynote, so the consumer can make an informed decision before purchasing if that wasn't the case? As they still allowed people to "pre-order" them.
All consumer electronics companies have agreements with media regarding the timing of reviews. Generally, in exchange for early access to the product, the reviewer must agree to not disclose anything about the product prior to a certain date.
This is good for the reviewer, as they get early access to the product and they get more time to actually test it prior to writing a review. Without this, there would be a mad dash to get the review finished as early as possible, and we would see a lot of reviews of products that were used for only a few minutes and that were not actually tested.
This is good for the company, as they get to dictate when the reviews all publish, thereby concentrating the discussion surrounding their product. This usually has the effect of having the products trend on social media, and gain more attention from consumers. Usually they want all the reviews to publish on the day the product is actually available for sale (not pre-sale).
Of course reviewers that write terribly unfavorable reviews are not offered early access for the next product, so there is some incentive to write a favorable review.
Of course, this has nothing to do with reviewers that just buy the product like the rest of us. Some companies, notably consumer reports, refuse free preview units per policy and only review units they purchase themselves. They cannot have a review ready as early as the rest for this reason. However, this makes their review less biased.
My point is there is nothing nefarious about this. You just have to keep it in mind when reading the review. If the review published the day a product launched, then it's probably a free early access sample. If the review published weeks after the product launched, then the reviewer probably bought the product. There is pros and cons to both.