Simple Ember.js Input Syntax

I'm seeing conflicting within the ember guides on how to go about actions syntax on an helper. I'm referring to the key-press and key-up parameters.

This section shows it without parenthesis as such:

Yet here (with the code snippet titled "app/templates/components/list-filter.hbs"), it does use parenthesis as such:

---

I'm not sure why the API docs leave out the parenthesis but the example puts them in. Any insight appreciated