Without the throttle stop screw, which keeps the throttle barrel in the carb body, you also would not have proper metering for the idle mixture. It's what rides in the groove and allows the idle needle to move in and out, metering the fuel at low throttle settings.

Some O.S. carbs have a separate carb retainer screw that only holds the throttle barrel in the carb body, and a stopper screw that's for adjusting the amount of rotation of the carb barrel. The .46 FX never had that kind of carburetor.