All of the stocks that Bill Hwang had in his portfolio were all extremely liquid stocks that trade on major exchanges with very good daily volume and good bid/ask spread. So by this criteria, IB would still take this "factor" into account when assessing how much margin to extend. I am not disputing that IB has active management practices in place but I have observed differences in lending practices extended to different sizes of accounts at IB perhaps according to these "factors" that you have mentioned. That you cannot deny. And in light of Bill Hwang's extreme wealth and taking into account of other "factors", I can speculate that IB would be lot more lenient in extending margins if he had actually opened accounts with IB to trade his portfolios vs to any average joe's.
And on the other hand towards retail investors, IB does apply more stringent margin lending practices that are unnecessarily restrictive to the point of damaging the profitability of retail investors anywhere from forced liquidations of profitable positions that were well within the margin limit to restricted position size for CASH-covered puts that uses zero margins. I have experienced them all personally and have suffered profit losses due to these so called "risk management" margin lending practices when I have already exercised very prudent trading practices that always included at least near-delta-neutral hedging and limited trading size that never used full margin. So excuse me if I call out the hypocrisy and double-standard of IB's margin lending policy.