It addressed several crashes and "quality of life" bugs that players encountered during the American Revolution campaign, particularly on the PC version.
While there isn't a narrative plot change in version 1.0.3, the update focuses on two main areas: Assassins.Creed.III.Remastered.Update.v1.0.3-CO...
The at the end of your string likely refers to CODEX , a well-known group that releases digital backups and updates. It addressed several crashes and "quality of life"
The "story" behind this particular update for is essentially a collection of technical fixes and visual refinements aimed at polishing the 2019 re-release. Assassins.Creed.III.Remastered.Update.v1.0.3-CO...