It sounds like FINCEN requirements require a 2-day settlement period. This period allows fractional trading to work (they pool orders and execute on day 2). Those same restrictions also appear to restrict a broker/dealer from using customer funds to cover this float. From there it's pretty easy to interpret the end results - risk rises, fees rise, and suddenly RH has to pony up massive amounts of liquidity to cover the DTC float.

Fuckery is certainly possible. This explanation still begs the question; at what point can a business decide not to cover the 'cost of doing business' and instead, create explicit downward pricing pressure.