The message I got from TDA says, "on or after September 3, 2021," so we will have to see if they restrict it tomorrow, or wait until after Sept 3, perhaps Tuesday Sep 7, when the market opens up again after Labor Day.
[Side note: when reading this just now, that it says "after September 3" does suggest that they *might* put off restricting buys for some time after that. Again, it is wait-and-see.]