I would report it if you got "you all" wrong. We do use "you all" or "you guys" when talking to a group so that the people you are speaking to don't all say "Who? me? or him/her? Oh.. I didn't know if you meant all of us or just me/him/her/them" :)
Duo uses "you all" or "you guys" to distinguish singular from plural 'you'. It is not meant to be translated and both are colloquial or regional expression not for general use. Actually, "you guys" is rather old fashioned, slang goes out of style like clothes.