Question:
Why does the Last Modified Date field at the component directory level have a different value than the Last Modified Date field on the Permission Set in Vault?
Answer:
The Last Modified Date on the Permission Set refers to end-user changes that have been made directly to the Permission Set within the UI. In addition to changes made to the Permission Set directly, the Last Modified Date at the component directory level can refer to system changes and indirect changes (such as Action Security enablement on an Object which adds permissions to a Permission Set).
The screenshot below is from the component selector for Migration Packages.
Note: At the component directory level, the Component Modified Date reflects the Last Modified Date on the Permission Set.
Related Documentation:
Vault Help Documentation: N/A