@BourdThat's a server issue, not a software issue. Your server setup, security policy, dictates the group ownership for script created files and folders. You'll need to check with your host on that.
ETA: MANY server setups will auto set ownership of script generated files and folders to "nobody" or "root" or www-data or similar -- which is "owned" by the server and not the user. They can still be read normally, but cannot be deleted or edited via FTP/ssh unless you have root privileges. It's security related.
