One alternative could be also to enable and report use ISC native change detection Enhancement: Native Change Detection - Announcements / Product News - SailPoint Developer Community
To regularly (during aggregation) identify and report all changes made outside of ISC.
If there are 30 k accounts, attempting to synchronize all accounts even a weekly basis would be very resource-intensive.
Or just add a before provisioning rule : that will set an attrbute lastSailpointUpdate in the plan for every operation on Active Directory.