Is "ego depletion" the only explanation for the experiment? How do the researchers rule out other explanations? Maybe people choose the cake because they think

Is "ego depletion" the only explanation for the experiment? How do the researchers rule out other explanations? Maybe people choose the cake because they think, "Phew! I did something difficult! I deserve some cake!" And the people who only memorized two numbers think, "Well, I didn't do anything that warrants cake. I'll just take the salad." I don't mean to propose this as an alternate explanation -- it just seems like there could be a million explanations for why people are more likely to choose the cake. (But maybe the researchers found ways to rule them out?) Another random question -- have people replicated this experiment? Just curious.