To create pagination we have to count all the galleries and it takes up some resources, so if you use just <!--PREV_PAGE--> and <!--NEXT_PAGE--> - we can save up a bit of server resources.
Here's an example
<pagination link_type="prev_page"> ... <!--PREV_PAGE--> ... </pagination>
<pagination link_type="next_page"> ... <!--NEXT_PAGE--> ... </pagination>
Pagination <!--PREV_PAGE--> and <!--NEXT_PAGE-->
Pagination <!--PREV_PAGE--> and <!--NEXT_PAGE-->
Don't forget to run script update