I have heard of a similar method. A person buries a cooler with the chestnuts inside and the cooler taped up and then buried inside a black garbage bag. They want the cooler top 6 inches below ground level. They store the chestnuts inside a sandwich bag with damp sphagnum moss on the nuts.
The cooler prevents freezing and keeps the chestnuts at a constant temperature.
Most of us have read threads where people bury DCO in the ground or in the garden with hardware cloth protecting them.
Along the same line. An all cooler has to be cheap to find and cost less than concrete and five gallon buckets.
My 2 cents ...