Steps to reproduce the issue

1. Edit file:
   libraries/src/MVC/Controller/AdminController.php

2. Find method saveOrderAjax()
   and comment out (so that we can use the DEBUG screen)
   \JFactory::getApplication()->close();

3. Enable debug and visit URL:
   /administrator/index.php?option=com_categories&task=categories.saveOrderAjax

(also same problem with menu items)
/administrator/index.php?option=com_menus&task=items.saveOrderAjax

Expected result

1 SELECT query to the categories table
1 UPDATE query to the categories table

Actual result

For N e.g. 300 categories in the table (assuming almost all of them belong to the com_conent)
300 SELECTs on the table
300 UPDATEs on the table

Code is here:
https://github.com/joomla/joomla-cms/blob/staging/libraries/src/MVC/Model/AdminModel.php#L1325-L1345

System information (as much as possible)

Additional comments