Good spot. I can find two bugs with the Matrix- one in the firmware, which doesn't observe the number of arguments its given leading to potentially undefined behaviour and all sorts of fun, and one in Rockpool which totally ignores the brightness you tell it to use, and just uses a fixed one...
D'oh!
This is a remnant from when we were testing just how bright we could drive the Matrix display without it eating the equivalent of the local power station. And a fine example of just how useless a "mental note" is when you're busy!