When you compare the two, they are like million years apart and totally different but quality principles can be applied to the software freelancer’s work process as well.
Note that the software freelancer doesn’t receive a spec sheet, “do this”. Neither did anyone go to a chocolate factory and told them “make it like this”. They have to figure out what to do and how to do it and why it’s ‘best’ done the way it’s done (or why it’s not good it’s currently done rather). And they could be totally wrong, and sometimes are.
The steps required to figure out the solution by communicating continuously with the end user, to build whatever is needed, and to manage and improve it over time, as well as to reconsider continuously whether your solution is still ‘on track’ with customer demands, is all part of a quality system.
In order to be successful in the long-term, whether you are a software freelancer, engineer, restaurant owner, or chocolate factory owner, you need to know how to set up and maintain a quality system. Even as an employee you can use quality principles to improve your work and work environment, you don’t have to be the owner.
Note that high quality doesn’t have to mean the chocolate has some magic ingredient that makes it taste ‘better’. To me McDonald’s is high quality: the food tastes like **** but it’s always the exact same taste in the same setting. The bathrooms are rather clean and the fries edible. So basically you know what you will get at McDonald’s with high certainty, whether you like it much or not doesn’t matter. Being able to deliver consistently whatever you deliver is what sets McDonald’s a million years ahead compared to most non-fast-food restaurants.