Mike you crack me up sometimes. Use your head man....air has to move up and over that choke horn. Remove that huge wall that air has to go around, and flow is made easier. No, it won't flow as well as a proper no choke main body, but it will flow better nonetheless. It's especially useful when you have to run a drop-base breather that puts the breather lid closer down on top of the carb, like the stock Fox duel snorkel does. There might be a half inch or so of clearance between the choke horn and the breather lid...but if you cut the choke off you gain an inch and a half of clearance, which is a lot less restriction for air to move through. It's a worthwhile mod if you don't NEED a choke, and you're too cheap to buy a proper main body. As far as how smooth the air goes into the venturies...it's not any less smooth than it was before the choke was sawed off is it? It's exactly the same thing, just shorter and less of an obstacle for air to travel over.
I ran a 650dp for years, ran awesome. I dynoed my 347 with the same carb i ran on my stock long block 302. The guy who tuned it was going on and on about how the duel plane intake i was running would only let me rev to 5500, and how the breather was gonna choke it out and on and on. Then it spun the rollers and he couldn't believe that it had just made more rwhp than another EFI 347 he had recently dynoed that had fancy aluminum heads on it. Then we took the breather off to see if it was choking power, and the A/F was all over the place and it put down LESS power. He said "whatever you do don't ever run another breather but this one".
When i got the cash, i stepped up to a Pro Systems custom built carb with a fancy NASCAR main body. I haven't been back to the dyno but between the carb and a Vic Jr. intake swap the car pulls way harder. I'm suspecting the gains are mostly from the intake swap though.
My old Holley
My new fancy pants Pro Systems 780
Oh, and i've started both of these carbs in the dead of winter...two pumps on the pedal, fires up first crank. Sure, it doesn't idle on it's own and you have to sit and goose it for a couple minutes to keep it running, but after two minutes or so it idles fine and once it warms up it runs like any other carbed car in the winter. If you WANT to run a choke, i'd suggest an electric over a manual choke. I got the manual because i didn't want to fool with wiring the electric, and i never used it so i took it off. I even spent the cash on a manual choke cable...waste of time. Just go electric and be done with it, or nothing at all.