This is true, though that said, on the flip side of things; exchanges like the one between the letter's author and the cat food company are exactly the sort of thing that helps expand one's understanding outside of their own domain of knowledge.
Be it out of hubris or genuine interest, that the author of the letter felt compelled to write to the company, they (and by extension us) received an insight into the decision making process behind one of the more mundane pieces of engineering we see on a daily basis (I certainly did)
It was a good reminder that creation of many things takes overlapping disciplines. It reminded me of a joke about a mathematician optimizing a farmer's operation. He returns after several months bursting with excitement, promises of improved profits.
Just because you're an expert at one thing does not make you an expert at everything.