Please note after much experimentation when using a VBO 'Modify Entity Values' with 'Select all items on all pages' checked (and using a pager) it will only actually modify the current page's entities even though you have 'select all items on all pages' checked. It will not change the entities on any of the other pages.
Just so you know if you have 'display all items' and hence do not have a pager the 'Select all items on all pages' selects all the items on that page and will modify the entities without issue, so it's definitely a pager problem.
At the moment I have over 9000 rows in a view so I really need this to work to make entity changes across all the rows with a pager. As you can imagine the greater the view grows the worse the performance if I have to display all (as opposed to page).