100% alcohol requires a molecular sieve or some weird extremely hazardous chemicals. Probably 90-95% alcohol is the max.
Maybe that neighbor meant to say “100 proof” instead of 100%...
You’re right. This still makes the purest drinkable alcohol like Everclear. It’s all stainless steel. His formula is twenty gallons of water, five pounds sugar and a block of brewers yeast. He gives it as gifts in liter snap cap bottles. You have to dilute it with distilled water to tone it down a bit.