For Captain Marvel this was a hassle and eventually some reviews had to be dropped from the site because people had been allowed to review prior to the rule change; presumably, this would not be an issue for future movies.
Originally, users were able to reveal their excitement or lack thereof in a project ahead of its release, but a couple of weeks ago, Rotten Tomatoes said it would be changing its pre-release function and that comments would be disabled until a movie was released.