The letter's core argument is that compute behaves unlike oil or wheat. "A GPU-hour exists only in the hour it is used," it says, and it can't be stored[4]. A data centre earns rental income hour by hour and an inference platform pays for compute on every model call, so their price exposure has no end date[1].
Hedging that with monthly futures means rolling from contract to contract, paying fees and taking timing risk each time. A perpetual never expires and is kept in line with its reference price by periodic funding payments between buyers and sellers, so one position can be held as long as the exposure lasts. The letter also points out that the news that moves compute prices, such as model releases, outages and export-control announcements, doesn't keep exchange hours[1].
It doesn't dismiss normal futures. Dated contracts still suit costs with a fixed end, like a training run booked for a particular quarter, and a strip of monthly contracts gives lenders the forward price curve they need to value GPU-backed loans[4].