Update notes need to genuinely reflect the changes in the build — generic "bug fixes and improvements" text on a version with major new functionality, or listing features that aren't actually included in the update, both violate this.
Usually a low-severity but real trigger when release notes are copy-pasted across versions without being updated to match the actual changelog.
"The 'What's New' text for your app update does not accurately describe the changes included in this version, per guideline 2.3.12."