all the lower beam wings (and rear wings in general) work together with the diffusor, in helping to extract more air from it (the diffusor).
The Williams wing, is most likely an effort to reduce drag, by reducing the frontal area of the car as much as possible.
There is probably a passus in the rules, that you have to use a "sort of" rear wing, so it was there interpretation of one.
You could see this idea (reducing the frontal area, by placing the wing very low) in other series as well. For a while many sports car, used or tried to use such a configuration in Le Mans.
And there where attempts at various times in F1 as well.
most of the true ground effect cars of the late70´s and early 80`s had the rear wings mounted much lower, to help the extracting of air from the venturi tunnel(s) and to reduce frontal area drag at the same time.
It was very interesting to see (at least for me), that this year in Monza, there was a different philosopy towards the Df vs. drag compromise.
For many years the low drag at all costs route was predominant, this year most teams opted for a bit more downforce.
Back in ~2003/4 when F3000 was the main support category for F1, the Lola in lowest wing settings had still too much DF/drag for Monza. As you where not allowed (by the rules) to take wings off, or make modifications to there fixing points and AoA, one team come up with the idea to mount the beam wings "upside down" reducing dag and downforce. It lead to a considerable gain in straight line speed, but was banned later on, and a team which still used the solution during the race, got dsq for it.
@ Richard
thanks for the heads up and correction in regards to the land speed records - much appriciated !!!
