Basically, yes; technically, not quite. The outflow that is posing serious risks is the flow from regional banks' check and savings accounts into brokerage accounts and then into repos/treasuries. It's unspecified if those brokerage accounts are at the same banks in question or at other institutions.

It's a good bet that the accounts are mostly at large brokerages and not at regional banks' brokerage services.

Doesn't matter much, really. The banks would have an issue either way.