However, I disagree.
Uhh I learned in the 2nd or 3rd grade that the teacher is always right and is GOD.
The correct answer is what the teacher says it is- if you want to pass.
As to wingtip vortices- keep in mind that the various winglets work by taking a lot of the vortex " energy " and redirecting it in such a manner that a few percent better lift is generated. Thus the improved takeoff performance. And in some cases, by ' reducing' the trailing vortex during landing, closer separation **could** be allowed for trailing aircraft.