If you press the ECO MODE button, the Multi-Information Display switches to HSI automatically. I don't remember reading about this "feature" anywhere in the manual or any other Toyota document.
May be I did not explain myself properly. If in the Multi-Information Display you have the Energy Monitor, for example, and you are driving in "Normal" mode (no buttons pressed), the moment you press the ECO MODE button, the Multi-Information Display switches to HSI, you don't have to use the steering wheel buttons to do this.