I should've read your post more carefully. I see now you're using an AutoNotification Event (not Action). In that case, yes, you'll only get a single title, text, person, etc., since each individual notification triggers a separate event; each event only covers a single notification.
Is your Task configured to allow multiple occurrences to execute at the same time? The default task setup is to abort new tasks with the same name, if an existing one is still running. That would result in your only getting the first notification if they come in rapidly enough. You'll want your task configuration to say "Run both together", not "Abort new task". Access that via the gear icon at the top right of the screen, when inside a task (i.e., where the task actions are listed). See if that helps.