Yes, I agree with you that the throat in the mouthpiece is the smallest diameter in the "entire air column" ... but the tip of the leadpipe (or mouthpipe) is the smallest diameter of the leadpipe and is known as the venturi (of the leadpipe). It would be correct to say that there are two venturii but in the explanation pertinent to reverse leadpipe I think you should to stick with the one.
To tell the truth I don't really think that "venturi" even needs be a part of your explanation for reverse vs standard tuning setups.
I can't imagine why anyone would send you nasty emails though; you are just trying to put forward a clear explanation so that someone can determine if they think they'd prefer a reverse to a standard (and of course you can't until you experience both.. "everything else being kept equal").
I'd just say that a standard setup has the male tube on both top AND bottom of the removable crook while the reverse has a male tube on the bottom and female on the top. Let them figure out what the theory is.
(Don't think everyone is in agreement of which is better and why anyway).