A review embargo is an agreement about when coverage may be published, and the date chosen is one of the most informative signals a publisher gives before launch.
The basic function is coordination
Reviewers need weeks with a game, and they receive it at different times depending on location, shipping and platform, which would otherwise stagger coverage unpredictably.
A common publication time removes the incentive to rush. Without it, an outlet that received the game early would publish first with a thinner assessment and take the traffic.
The embargo therefore protects the quality of reviews as much as it serves the publisher, which is why most outlets accept the arrangement.
Access is the leverage that makes it work
Publishers control who receives early copies, and an outlet that breaks an embargo is usually removed from future distribution lists.
That is a meaningful commercial threat, since coverage published a week after launch reaches a fraction of the audience of coverage published on the day.
The agreement is rarely a contract with teeth. It functions through a relationship that both sides expect to continue.
Timing relative to release is the real signal
An embargo lifting several days before a game is available lets buyers read reviews before deciding, which a publisher only permits when confident.
An embargo set for the moment of release, or after it, means preorders and launch-day sales occur without published assessment, which is a choice with an obvious motivation.
Experienced readers treat a late embargo as information, and outlets increasingly state the timing explicitly for that reason.
Online games complicate the whole arrangement
A game whose servers only populate at launch cannot be assessed meaningfully in advance, because matchmaking, stability and load behaviour are the parts most likely to fail.
Publishers sometimes hold reviews for that reason rather than a defensive one, and the two cases look identical from outside.
Outlets have adapted with staged coverage, publishing early impressions under one embargo and a scored review after the servers have been live for several days.
Conditions attached to access are the larger issue
Some arrangements go beyond timing and restrict what may be discussed, what footage may be shown, or which story elements can be mentioned.
Spoiler restrictions are usually reasonable, but restrictions on discussing monetisation or performance shape the coverage rather than merely scheduling it.
Disclosure is the accepted response. An outlet that states the conditions it accepted lets readers judge how much the coverage was constrained.