I was wondering if there is a minimum age required to apply for a z visa?

Hello,
I got a job offered as a bar/ restaurant manager. My company informed with a local agency if there was a chance for me to get a z type but they said I have to be minimum 24yrs old and I am only 23. Now I heard stories about people actually working legally on a z under 24 yrs old. Based on what do they give z types to people under 24yrs old? Is it actually possible?