Back to basics then
Yet again, according to the posts an engineer decides that "riding the brakes" is, well, just a non event really and then guess what? Erm he / she is there for a purpose and the purpose is to stop "xxx" tons of aircraft should any of a number of potential incidents arise.
The shear pin is supposed to prevent excessive loading on the nose u/c and hence, when it does fail for whatever reason, the idea is that tug and remaining bar continue safely in one direction and a/c comes to a halt without damage and with the other bit attached, usually the towing head. Had the experience a few times and, whilst it comes as a shock, if you are actually sitting in the seat and monitoring the tow, with your feet resting on the pedals and one hand on the parking brake----well, there isn't a lot of paperwork to contend with afterwards.
Sorry, but IF it is true that said eng was down the back then no sympathy for him / her.