Correct. Many of the sealed cases at the Federal level are only search warrants for electronic information (wiretaps, emails, texts, etc). Many of THOSE are requested by State/local govt agencies in support of their investigations.
The # of "indictments" might be as high as the numbers projected in the sealed cases, but it would be spread across the Feds and the State courts.
The "sealed indictments" crowd does not have a very good understanding of how the legal system works, so they've misinterpreted the sealed cases to be indictments only. Again, I'm not saying there aren't a shitload of sealed indictments, I'm simply saying they are not all Federal.