The same director noted that the SI%, according to their way of calculating*, is actually at 55% (still very high). And like the poster below stated, one cannot really know the difference between a borrowed and "ordinary" stock .

Webull came out and clearly stated that their clearinghouse had issues with putting up collateral for the tickers and thus had to shut them down [0]. And while Robinhood has not come out directly and said it was due to liquidity, one can easily gather that from the statements they put out, the new funding they needed, and lastly the fact that DTCC required higher collateral for those tickers.

[0] https://www.wsj.com/articles/gamestop-trading-restrictions-b...

* It includes all tradeable share. So in the case of the example, normal SI% states 2:1, two shorters and one original share. Their way is 2:3 which is, 2 shorters (B,D) and 3 longs (A,C,E)