Hmm...I do not see in those links where a sub-minimum stipend is allowed except in the case of high school vocational training. Can you quote it? (Criteria #6 appears to indicate no wages permitted.)
Theres a distinction between stipends and wages, and while I can find lots of third party sites whose general character and other information suggests general reliability referencing the option to pay a stipend to trainee interns (while also warning of the need to assure they aren't structured as wages), I cant find an authoritative DoL source articulating a standard or test (or giving examples) distinguishing them.
Thanks for looking. I've never heard of it happening, but all sort of arrangements happen in the grey areas of the law. I've been stipended before as an intern, but under the understanding that my hourly "wage" would not drop below the minimum.