WP_User object behaving strangely when used inside Admin Panel?

Question

I'm building a custom settings page in the WordPress Admin Panel and I'm pulling some data from a WP_User object at one point. I've used this object dozens of times in the actual theme, but in this case I am not seeing the same behavior. The "object" is in $user, and when I try to use $user->display_name to retrieve the display name, I am told that I am trying to get a property of a non-object.

Here's the relevant code:

$userID = $assignment->user_id; //existing user ID is passed correctly
$user = get_user_by('ID', $userID); //should work fine...
print_r($user); //clearly shows an WP_User object in the output
echo gettype($user); //returns boolean
echo $user->display_name; //says I am trying to get a property of a non-object

Here's the output of print_r($user):

WP_User Object
(
    [data] => stdClass Object
        (
            [ID] => 1
            [user_login] => name
            [user_pass] => $somehash
            [user_nicename] => name
            [user_email] => [email protected]
            [user_url] => http://example.com
            [user_registered] => 2017-11-21 17:05:00
            [user_activation_key] => 
            [user_status] => 0
            [display_name] => bobsmith
        )

    [ID] => 4
    [caps] => Array
        (
            [member] => 1
        )

    [cap_key] => wp_capabilities
    [roles] => Array
        (
            [0] => member
        )

    [allcaps] => Array
        (
            [activate_plugins] => 
            [create_roles] => 
            [create_users] => 
            [delete_others_pages] => 
            [delete_others_posts] => 
            [delete_pages] => 
            [delete_plugins] => 
            [delete_posts] => 
            [delete_private_pages] => 
            [delete_private_posts] => 
            [delete_published_pages] => 
            [delete_published_posts] => 
            [delete_roles] => 
            [delete_themes] => 
            [delete_users] => 
            [edit_dashboard] => 
            [edit_others_pages] => 
            [edit_others_posts] => 
            [edit_pages] => 
            [edit_posts] => 
            [edit_private_pages] => 
            [edit_private_posts] => 
            [edit_published_pages] => 
            [edit_published_posts] => 
            [edit_roles] => 
            [edit_theme_options] => 
            [edit_users] => 
            [export] => 
            [import] => 
            [install_plugins] => 
            [install_themes] => 
            [list_roles] => 
            [list_users] => 
            [manage_categories] => 
            [manage_links] => 
            [manage_options] => 
            [moderate_comments] => 
            [promote_users] => 
            [publish_pages] => 
            [publish_posts] => 
            [read] => 1
            [read_private_pages] => 
            [read_private_posts] => 
            [remove_users] => 
            [restrict_content] => 
            [switch_themes] => 
            [unfiltered_html] => 1
            [update_core] => 
            [update_plugins] => 
            [update_themes] => 
            [upload_files] => 
            [member] => 1
        )

    [filter] => 
    [site_id:WP_User:private] => 1
)

Worst case, I can query the database and pull the value like that, but is there any reason why WP_User doesn't seem to behave the same in the Admin Panel?