When the brake is pulled the two pads come together BUT the arm on the non drive side is pull upwards (or towards the front of the bike I guess, which means it gets pulled towards the paet of the frame housing the bottom bracket). When pulled the brake arm is pulled towards the frame and before the brake is fully pulled the arm fouls the frame at that point.
In order to reduce the amount the arm has to be pulled he has added spacers to the brake pads to move the pads closer to the wheel, meaning they engage quicker, the arm is not pulled as far and the arm does not reach as far as the frame ... thereby not hitting the frame at full pull but allowing full braking.
At least that's my take on it.
https://www.pbandjcoaching.com https://www.thisbigroadtrip.com