According to FC Stone their commercial customers delivered over 2 tcf of natural gas last year. Total US usage is around 27 tcf so just shy of 7.5% of total. Makes you wonder if they used their knowledge of optionsellers book to facilitate the squeeze and make a windfall on their otc and commercial side. The losses and uncollectible debit balances could be dwarfed by the gains on their own book. That would make more sense then their own internal risk management systems being ran over.
https://www.intlfcstone.com/Commodities/Energy/
Apparently FC Stone said their commercial clients were rattled by the "rogue wave" too but they all met their margin obligations. And that is illegal. That's called front-running.