The issue you're experiencing with highlighting text in OneNote for Mac could be related to the specific functionality and limitations of the OneNote application compared to other Microsoft Office applications. While double-clicking to select a word and dragging to highlight text works in programs like Word, Outlook, and PowerPoint, OneNote may have different mouse interaction behaviors.
Unfortunately, the context provided does not specify the exact reasons for this limitation in OneNote for Mac. It's possible that the application does not fully support the same text selection methods as other Microsoft Office applications. If this functionality is critical to your workflow, consider providing feedback to Microsoft or checking for updates to see if this feature is improved in future releases.
For now, you might need to use alternative methods for selecting text, such as clicking and dragging to highlight or using keyboard shortcuts for text selection.
References: