In ArcGIS Pro, when using the Create Mobile Map Package tool and checking the 'Keep only the rows that are related to features within the extent' option, the resulting mobile map package has all the attachments.

Workaround

1. Select features inside the current display extension or area of interest.
2. Then, right-click Feature Layer and open Export Features. Click the Environment tab, check the 'Maintain Attachments' option, and click OK.
3. Only the attachments from the selected feature appear in the exported data.
4. At the end, use the exported feature layer to create a mobile map package.

Steps to Reproduce