No? This will search the logfiles (if irssi is configured to create those at all) for a pattern. This still requires that you had to have an irssi client running and connected to the server/channel in question, during the time the user is afk. Which is why others recommend e.g. setting up ZNC.
Yes they are wrong. A contribution may consist of “merely” a bug report. Even just asking questions may indicate that the UX or documentation is lacking.