From Wikipedia, under "Systemically important financial institution" and at the end of the discussion:
"Asset Managers
It is widely anticipated that the Financial Stability Oversight Council will eventually designate certain significant asset managers as nonbank systematically important financial institutions (Nonbank SIFIs).[18] The FSOC recently asked the U.S. Treasury Department’s Office of Financial Research (OFR) to undertake a study that provides data and analysis on the asset management industry.[19] The study analyzed the industry and describes potential threats to U.S. financial stability from vulnerabilities of asset managers. The study suggested the industry’s activities as a whole make it systemically important and may pose a risk to financial stability. Furthermore, it identified the extent of assets managed by the major industry players. This request for the study is considered by some as a first step in by the FSOC in reviewing the industry and individual player to determine which are systematically important. Once designated as systematically important those entities will be subject to additional oversight and regulatory requirements.[18] In 2013, the Treasury Department's Office of Financial Research released its report on Asset Management and Financial Stability, the central conclusion was that the activities of the asset management industry as a whole make it systemically important and may pose a risk to US financial stability. Furthermore, in 2014 the Financial Stability Board and the International Organization of Securities Commissions issued the Consultative Document which proposed methodologies for identifying globally active systemically important investment funds. Both reports further the conclusion that is likely the U.S. Financial Stability Oversight Council will designate a few large US asset managers as systemically important.[20]"
So based on that is sounds like it very well could apply to some asset managers, and Vanguard is certainly a very large asset manager...