IMO what the article talks about is the business model, not the culture, they are two separate things - not entirely separate, but mostly. Business model is Apple shipping devices and Google providing ad-supported services over the Internet. Culture is how in one company you can't push changes to the central repository without a code review which might take a couple of days, while in another you can work whichever way you please but if things break you're expected to fix them on Sunday at 3 AM.
Like the business model, culture is certainly influenced by the people at the top, though I think it's defined by a somewhat larger number of early employees, and it's harder to change once established, compared to the business model. Both affect performance in the market, but it's not as straightforward to analyze, even in hindsight, how exactly culture affects market performance relatively to the business model where in hindsight it's perfectly clear.
It's discussing and means to be discussing organizational culture. The business model, controls, and processes are artifacts of the underlying hidden culture. This is what the beginning of the article is discussing, when it talks about going three degrees down. Think of Conway's Law: An organization is constrained to design systems that mirror its structure. This is basically the same thing, but abstracted a level; the organizational structures themselves are constrained to be shaped by the business' underlying assumptions.
("Tech culture", such as your example of code reviews, is usually an example of controls and processes. What controls and processes exist for creation and deployment of software? If we were making widgets on the factory floor instead, the fact that these aren't "culture" as being discussed would be more immediately obvious.)
Like the business model, culture is certainly influenced by the people at the top, though I think it's defined by a somewhat larger number of early employees, and it's harder to change once established, compared to the business model. Both affect performance in the market, but it's not as straightforward to analyze, even in hindsight, how exactly culture affects market performance relatively to the business model where in hindsight it's perfectly clear.