How to disable thermal policy for the icloud photo process?
While the error messages are still present in Console, the Photo app is able to sync changes in the Photo library in iCloud after upgrading maxOS to version 10.15.6 (19G2021).
I find out that the real reason is not the upgrade itself. Actually it is due to the fact that I disconnect my external monitor during the upgrade.
I typically use my MBP with both of its primary monitor and an external monitor turned on. It triggers the thermal throttling which stops the iCloud photo sync from happening.
Whenever I disconnect my external monitor, the icloud sync will succeed.