I think his exact number, 5%, may be a little low, but the sentiment is right. The article is addressing the change from programmer to entrepreneur, and I think

I think his exact number, 5%, may be a little low, but the sentiment is right. The article is addressing the change from programmer to entrepreneur, and I think it is very common for technical founders to care too much about what they are most experienced with: the code. He even acknowledges the importance of code quality ("It has to be high quality code that isn't filled with bugs or is insecure.") but his point is that, as a first-time entrepreneur, you will be overwhelmed with the other aspects of a business that have to developed, and you will tempted to focus yourself in the area that you have specialized in for years prior. As a founder that has recently began the transition from programmer, I can certainly say there are times that I've failed at this, and I'm sure it happens a lot.