Some rear carb designs do this to a level viewed as a lot but most all carbs spit some fuel, especially when they are subjected to forward motion and exposed to the open air. Even with a velocity stack you encounter the venturi effect of moving air over an open tube, so total elimination of "spitting" is all but impossible.

New engines are not "factory tuned" and are likely to be quite rich in the lower RPM bands. The richer the condition the more excess fuel available to be pulled out of the carb throat. This requires user input to correct. Tune the engine, which is something every engine requires, and is also something that has been described in extreme detail a great many times in this and other forums.

Another condition that generates a lot of fuel blowback is worn or broken reeds, or reeds that fail to seat correctly on the cage frame. However, this is not something common to new engines and generally only seen with engines that have been in use for some period of time. A good general rule is that the better the engine the longer the reeds will remain functional. So it can be a bit brand specific.

One more item that can impact the amount of fuel departing the wrong side of a carb is the metering needle height inside the carb. Since carbs are now manufactured and assembled by cheap overseas or Mexican labor it's impossible to know if the carb was assembled correctly without performing a full carb teardown. With modern day outsourcing to foreign countries I see poor assemblies in as much as 50% of the carbs passing through my hands. I doubt even the best engine manufacturers get any better with current Walbro products. Can't say for Tillotson since they are based in Ireland and may use different manufacturing and assembly methods. The cloned Chinese carbs have a much higher error factor.