That's entirely possible and even likely, but that's still a huge market failure that should be corrected. You can't have a situation like this happening to some stocks exclusively.

Where were those increases in required DTC collaterals when TSLA/NIO/your favorite SPAC was going through the roof? The conspiracy just moves to whoever unilaterally decided to raise collateral requirements from 2% to 100% -- a 4900% increase, and nice and whole numbers that seem fully arbitrary. A situation in which people have settled in their accounts should not depend on some backdoor credit wizardry that ultimately damages retail investors.