The fuel in the carb can not drain back into the tank
The float needle seat is at or above the level of fuel in the bowls and can't syphon once the level is below it.
I suspect you have some other issue as A/J noted.
You can test all this out.
Next time you suspect fuel has drained back. Pull the air cleaner and pump the carb, look down the bore for fuel from the accelerator pump.
You might be having some fuel quality issues as well. Alcohol blend fuels are problematic in our cars.
I had a problem when the engine was HOT, accelerating from a light it would start to die then letup on the gas, and it would recover. Then ease back on the gas and it's all good.
I switched to alcohol free gas and I can't make it happen any more!