There have been multiple instances in the Endwalker story mentioning that the "Blessing of Light" instead of the "Echo" is the one that has been protecting us from being tempered.

This would against the events/instances that happened in previous expansions.
Please remember that Fordola has an artificial echo that let her defend herself against the tempering. She doesn't have the Blessing of Light just like Arenvald.
They both have the Echo, though not the same kind, and that's the thing that helped protect them.