On my 2016 headset, I had to remove two additional Phillips screws at the top (appear in picture) and two more at the bottom (which are not present in the headset pictured here, must be a different revision) before the sensor array comes off.

It was a T6 that fit perfectly in mine, T5 didn't cut it. Maybe it's a revision thing? Mine was an early model from 2016.
Edit: Edited guide to say T6.

Mine was pretty tight so I had to force my plastic spudger into the opening to get anywhere