150 proof? I don't think I've ever heard of a yeast that can survive 75% alcohol, pretty sure that's one of the BIG reasons for distilling. I also don't think that any part of the rind has enough sugar in it to feed yeast.
Sounds more like he did an extract or tincture. The broad strokes of the two methods is putting orange peel into a high proof liquor, like Everclear or another pure grain alcohol, or any of a number of rums and vodkas.
Just using the peel would result in something high in aromatics, but low in flavor, and even the most careful removal from the pith can still leave some puckering qualities.