I'm not an engine guy, but here are a couple thoughts to mull over. It's possible that you may want turbulent flow to mix the charge better as it enters the case and then ports. In 100cc kart engines, we found that polished transfer roofs worked noticably less well than rough ones in getting the charge into the combustion chamber (maybe it just allowed it to burn better or cut exhaust losses). Also, turbulators on wings allow flow to conform better, really changing HLG flight characteristics. So, might it be possible that the sharp transitions mix the charge better? 'just wondering...
For stunt, it's actually critically important, far more important than the volumetric efficiency or flow per unit draw. Not changing flow characteristics with changes to the load or the input air direction/velocity. This is what leads to the unexpected phase changes/apparent mixture changes. Since you don't really care how efficient it is and you can get arbitrary amounts of power almost no matter what you do to the venturi, my opinion and experience has been that almost anything you can do to improve mixing or make it insensitive to maneuvering, the better. That's why you want diffusers on the input, and, if there was a way to do it, you might want a large plenum as an airbox.
One of the reasons the ST46 runs so smoothly is that the internal shape of the venturi is *not* smooth, making the otherwise very undesirable "flush fuel inlet" work OK. In the stock venturi, the fuel comes in through 6 holes that reside in the lee of a sharp edge, where the flow is almost certainly very turbulent and relatively low velocity.
Note that the fuel suction is only one side of the equation - it also matters how hard it is to suck the fuel through the plumbing. Completely conventional plumbing has to flow at most about 1.5 ounce/minute on average (8 ounces for a pattern), that doesn't mean it flows freely enough to keep it from unexpectedly going lean, because the required peak flow is much higher than the average. This is the problem with 4-strokes running conventional tanks and thick fuel, but it also happens on the larger 2-strokes.
There, that ought to get the spirited discussion started again.