Did you not read the tweet or are you just trying to misrepresent her argument? She is asking why different sets of trading rules are apply to retail and institutional investors. If retail can sell, but can't buy, who are they selling to?
"We now need to know more about
@RobinhoodApp’s decision to block retail investors from purchasing stock while hedge funds are freely able to trade the stock as they see fit."
Does she or doesn't she say that the retail services allowing sales but freezing purchases are especially worth of investigation, compared to the general category of retail services freezing stock purchases?
Of course, in reality, the only services freezing stock purchases are those allowing sales but freezing purchases. Because freezing sales in addtion to purchases would be much more problematic, not less.
"We now need to know more about @RobinhoodApp’s decision to block retail investors from purchasing stock while hedge funds are freely able to trade the stock as they see fit."