This module is so useful that it could use it's own drush command to run the update existing nodes script.
Drush help might describe the feature like this:

drush cnr-up
Update nodes having corresponding node reference, to synchronize node references.

Example: drush cnr-up --batch-size=50 book author store

Arguments: node types to update corresponding node references

Options:
-- batch-size Number of nodes processed in each batch