The additional air in the head space might delay the beginning of fermentation, but that means more yeast cells. Once the fermentation starts, the headspace will be full of CO2.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk