You are nuking it way too much. See my reply above. The drop in pressure on the back side makes for a better vacuum signal for the map and also more or less helps "pull" the air through the throttle body. If it was such a bad design to use a venturi then why are stock throttle bodies designed with a venturi effect? They would just use a straight metal tube with a simple valve in it.
There is a bit of misinterpretation of fluid dynamics in that.
Stock throttle bodies aren't designed with a venturi effect, they just happen to have one. It's due to the design requirements of having a single throttle body regulating air into the plenum rather than having an individual TB for each cylinder. As a result, a venturi effect simply happens because of the restriction followed by a large volume which allows the air to return to normal condition before being taken into each cylinder runner.
The TB is tapered to reduce turbulence so that the air inside the manifold is in a laminar flow rather than turbulent flow. The smaller TB compared to plenum is so that the individual runners can extract air from a common mass pressure within the plenum rather than differential pressures resulting from air entering a TB the same diameter as the entire plenum (nearly a 10" diameter TB) and traveling different distances to the cylinders with a varying velocity.
Your comment about the MAP sensor is very telling because it means that a modified TB creates an artificially low vacuum at the MAP sensor tricking the computer to think it has more airflow than it really does so it adds fuel. The same thing can be done by adjusting the A/F ratio with a predator.
By your explanation, the modified TB is little more than a trick to get the computer to change A/F ratio and has nothing to do with the venturi effect on the engine airflow other than it changes the vacuum pressure at the MAP. Similar to moving the IAT to the airbox so that it thinks the inlet air is cooler and more dense than it really is.
If that is the true explanation, then just get a predator and tune the engine properly with real data for maximum performance...for nearly the same price.