Do Subagents Background Themselves in a Headless `-p` Run

You write a claude -p "review these 5 files" script that dispatches 5 subagents, expecting them to fan out concurrently the same way they would in an interactive session, then exits once all 5 report back.

By default, do those subagents run in the background in this headless, non-interactive -p invocation the same way they would interactively?