Nitpick: your comment implies that the DTCC is representing Wall Street, but it is an understatement: DTCC for all intents and purposes is Wall Street. DTCC is owned by (quoting wikipedia here - sic!) "banks, brokers". It's a 6 minute walk from NYSE to DTCC (which shouldn't be surprising).

Given that, it isn't outside of realms of possibility that raising of collateral requirements had additional objectives other than simply limiting risk on the system (which, I should mention, was very, very real - in case RH went bankrupt). Normal people won't have any way to know.