I could certainly be wrong but I'm thinking it was a typo. I believe what was meant was "Primary and Secondary FILES".
Henrico Bekker ... can you verify, please? And if you really did mean "Databases" and not "Files", then I agree with Bret... do you have a reference link because I've never heard of "Primary and Secondary DATABASES" before. EDIT: SEE THE NEXT POST BELOW FOR A CLARIFYING LINK!
Shifting gears a bit, this IS a really cool feature because I have predominately batch-oriented databases that would benefit from a higher max dop and busy OLTP databases that should be relegated to a lower MAXDOP on the same box. In the past, my rule of thumb was MAXDOP <= Core/4 < 8 . I can tweak the hell out of that when we get to 2016 in a couple of months.
Another really helpful 2016 feature for databases that haven't yet been brought up to snuff to fix years of legacy development and poor coding practices that causes the bad form of parameter sniffing is the new ability to clear proc cache at the database level.