The rating represents further potential evidence that the long-in-development title could finally be approaching a launch date, nearly ten years after development is understood to have began.
There have been other potential signs the game could be nearing completion, most notably via a leaked Skull & Bones video in April which provided an overview of what players can expect.
According to the six-minute video, the game is set in a world inspired by the Indian Ocean during the golden age of piracy.
Players begin their journey as an underdog whose goal is to become the most infamous pirate to sail the seas.
Skull & Bones was first revealed by Ubisoft at E3 2017, with a release date set for the end of 2018.
It was then delayed to 2019, then March 2020, then the fiscal year ending March 2022, then the fiscal year ending March 2023.
Then last month, Ubisoft said the long-delayed game will be released during the second half of its current fiscal year ending on March 31, 2023, and it recently said that the title is now “multiplayer first”.