OneNote Interop API UpdatePageContent changes lastModifiedTime of unmodified child elements

You are changing an Outline by adding an OE, but UpdatePageContent refreshes lastModifiedTime on the Outline’s child OEs, erasing the per-author timing you expected to preserve. Microsoft documents the page-level object as the update unit: only changed outlines, images, or ink must be submitted, but it does not guarantee that EditedByAttributes on descendants remain unchanged when their parent Outline is rewritten. The expected-last-modified parameter prevents overwriting a page changed since it was read; it does not preserve child timestamps. force=true controls handling of unknown data, not auditing metadata. The workaround is to avoid round-tripping an Outline containing audited siblings. Add new content as a separate page-level Outline where layout permits, or store author/time data in your own metadata. Reproduce the issue with minimal XML on a OneNote build and report the before/after XML, schema version, and build to Microsoft. There is no documented API switch that preserves those child timestamps