Fuel spitting of frothing at the entrence of the carb has more to do with fuel volume/weight than anything.
The air is being pulsed at a high frequency, the fuel has weight and doesn't start and stop so easily, so what we see as a result is the fuel being forced back out into the open. It has weight and momentum so it has to go somewhere. The next pulse of intake air will have a head start on a fresh supply of fuel rich air mixture.
The engine is usually tuned for maximum power, so this effect normaly isn't an issue. Unless of course we are looking for fuel economy.