Legally, IRDs and futures trade/settle on a few centralized exchanges with maybe one CCP (at least going by clarusft numbers on monthly dv01 volumes [some products way trade more on different venues compared to others], esp compared to all the places USDT trades) with many times rehypothicated US treasuries or other gov bonds behind it all, scheme blows up occasionally (was fun watching 30 year UST's trade ~30 bps under 75% of SOFR txs for a month before sept 2019 'surprise' fireworks happened).
> … buy one billion Tether
With no slippage/spreads on dex's or cex's to be able to do this with any stablecoin? Pipe dream. Maybe you can market make over the course [unknown amount] of time and pick it up on cex/dex's at/under $0.9989, but good luck trying that everyday (esp on chain where you will need to split that over many address all the time or addr tracking algos will front run if the MEV bots dont get you on every tx).
Shit show all around, ones just more concealed from the public and "regulators" than the other…