Why this query explains does not contain "use where"

Question

I am testing requests for my site (development), but I found that there is something strange that I don’t understand, look at the Red Star line - why does this request explain that it does not contain "using where"

Can anyone explain about this? Thank you very much

mysqldump sample download (zip 46.9 MB): https://drive.google.com/open?id=0B3ve2F7eRJk4eUJteXppRVYzMk0

MariaDB 10.1.9 - InnoDB engine