From the letter:

We believe such a rulemaking is necessary to provide much-needed clarity to this thus-far opaque part of the U.S. financial system – that is, the manner in which parent companies and affiliates of ILCs are subject to any kind of federal regulatory or supervisory oversight. By contrast, the federal statutory, regulatory and supervisory framework for parent companies and affiliates of ordinary banks is fully transparent and quite clear. We congratulate you and the FDIC staff for doing this important work, and for soliciting public comment on it.