Exactly. That’s how it works. If you expect your agent plugin to run for 5 minutes, it would be appropriate to put it into a 6-minute-directory (360), but not into 240.
Furthermore: if the plugin gets killed or exits in time but with a bad return code, then its output is discarded. That’s different from the behaviour of “non-detached” plugins. If they, for instance, exit 1, the rc is ignored and the output is sent to the server. If the very same plugin is run from a subdirectory, the rc is honored and its output is discarded.