Why does a clean configuration lead to the generation of greater wingtip vortices? "Slow, heavy, clean" are the three major conditions generating stronger wing vortices. It's very clear how "slow and heavy" aircraft create stronger vortices, but why a "clean" configuration generates stronger wake turbulence is less clear. 

I did some digging on this, and found some people saying "use of the flaps reduces the AoA and thus leads to weaker wake turbulence" and others claiming "use of flaps moves the center of lift toward the root of the wing and that leads to less lift around the tip of the wings and thus less wingtip turbulence. 

Which explanation is correct? 

Edit) I checked the answer given here What is the relationship between angle of attack and wake turbulence?, but I'm not really sure "not really" is the right answer to this. The AIM (Aeronautical Informational Manual) is very clear about this, designating "clear" (along with "heavy," and "slow") as one of the three factors that increase wake turbulence.
I would actually assume the opposite to be true. 

Let us assume the vortex intensity and the induced drag are directly correlated. The induced drag coefficient can be expressed as:

$c_{Di}=\frac{c_L^2}{\pi\cdot AR \cdot e}$


$c_L$: Lift coefficient
$AR$: Wing aspect ratio
$e$: The so-called Oswald factor, a number which equals one for elliptic lift distributions. It decreases for distributions that deviate from the elliptic one.


Most wing designs aim to achieve an elliptic-like lift distribution in order to minimise induced drag in clean configuration. 

As flaps, spoilers, air-breaks and so on are deployed the lift distribution will deviate substantially from the elliptic one (see diagram), hence reducing the $e$ factor and increasing the induced drag. If the first assumption still holds, an increase in induced drag will have been caused by an increase in vortex intensity.



Additionally, significantly higher lift coefficients can be achieved with deployed high-lift devices, which also contribute to increase vortex intensity.