You are correct.

Nowhere did I see it said on my sources on grand juries but I looked up the Wikipedia for the DC Sandwich Guy case and: “U.S. law typically gives the Justice Department 30 days to secure an indictment after an arrest.”

https://www.reuters.com/legal/litigation/grand-jury-declines-indict-man-arrested-throwing-sandwich-us-agent-source-says-2025-08-27/

(this is the source cited by Wikipedia but seems to just be stated without source itself in the article)