Core_user_get_users_by_field does not return field "username"

Hello! 

I am using a web-service to get user information. On the new untuned server (screenshot #2) field is return, but not on the old server (screenshot #1).  I only have a username and password, and also a token of Moodle after request in "...\login\token.php" and I cannot get user information in other ways than by "username". Pehaps you know why function didn't return field "username"? All permission are granted.