And to give some insights into why that is the recommendation here: data/es (or more recently data/es5) is where the backend data is cached for better performance (especially when searching data). Any server install/migration, or any database URL swap, should be accompanied with a proper rebuild of that data cache, otherwise there’s a risk of having data out-of-synch with what is truly persisted in the database.
The approach when gives this recommendation to rebuild ES data is: stop SQ, delete data/es5 , restart. Note that subsequent startup may take slightly longer than usual, due to ES data rebuild. Be aware that none of this is a usual operation, and it’s always better to investigate it first as you did here.