I'm going to repeat myself. There is no requirement that brokerages are slow to settle. There is a requirement - the one you linked - that a brokerage may not

I'm going to repeat myself. There is no requirement that brokerages are slow to settle. There is a requirement - the one you linked - that a brokerage may not take MORE than three days. It does not require them to take three days. A brokerage can settle as fast as it can.