For some reasons it’s useful to tell WordPress it’s an older Version than it is. Maybe as well a newer version? I don’t know any case for a newer version…
Reasons for an older version can be pretending to need an update/upgrade. Or you want to test wp-cli update tools and you don’t want to setup a new WordPress.
You can set the WordPress version easily in your
/wp-includes/versions.php file with by changing
$wp_version = '5.3';.
PS: Be careful. It can damage your WordPress.