> the process of liquidating and transferring securities is much slower than ACH or Zelle.

That doesn't seem relevant here. The account disappeared due to a data maintenance error; it wasn't extracted via a legitimate transfer to another account, they literally forgot about it.

Yes, that is why I caveated my comment. But her quote is still a good reason to point out that if there is a chance you might need access to money within short notice (I’d say within a month), it should be in a checking or savings account.