Difference with other bulk opertions?

The difference is that with this you have the option to only edit the field if it didn't have a value (which is a condition that you could copy in a VBO action only with custom code, or by using eca_vbo module), and the benefit of not having to filter and select the entities to update: you automatically update all the entities that have that field, directly from the field settings form, so I would say it's pretty convenient for this specific use case, ie. when modifying the structure of your site (more specific than with VBO).

Thanks.
Maybe add this info to the module page.

Updated project page, thanks both!

Automatically closed - issue fixed for 2 weeks with no activity.