The first statement of the "Update and Overwrite" section says:
-update is used to copy files from source that don't exist at the target, or have different contents. -overwrite overwrites target-files even if they exist at the source, or have the same contents.
The "Command Line Options" table says :
-overwrite: Overwrite destination
-update: Overwrite if src size different from dst size
Based on the implementation, making the following modification would be more accurate:
The first statement of the "Update and Overwrite" section:
The "Command Line Options" table: