If you edit the front page settings and change frontpageloggedin to contain a "Combo" item, the administrator will experience very slow loading of the /index.php page if the site has many courses.
Example: site with 6000 courses taking 2 minutes to load /index.php and placing high load on the database server.
The "Courses list" front page item does not suffer this problem.
The relevant code seems to be:
echo $OUTPUT->heading(get_string('courses'), 2, 'headingblock header');
$renderer = $PAGE->get_renderer('core','course');
Could that course tree be changed to not show all courses for admins?