"X makes money, therefore they are not a tech company" seems rather oversimplified in the same way "X is a tech company" is oversimplified. Actually, it seems oversimplified to the point of maybe not being so useful.
I think the way most people would define "tech company," if they were pressed to offer a definition, is that a tech company is one that derives the bulk of their revenue from selling technological goods and services, rather than using technology as the means to sell other goods and services. There's no way to keep that definition from being somewhat fuzzy, but if I say "Dell is a technology company and Cadbury is not," I don't think people will really object to that unless they're trying to be pedantically clever about it: Cadbury may use technology in all sorts of clever ways to manufacture chocolates and get them to retail shelves, but they're selling you chocolates.
There are obviously companies that complicate this by having multiple divisions with different kinds of revenue streams -- Amazon and Apple both come to mind immediately -- but Netflix really isn't one of them. What they do requires a lot of focus on their technology, and from the perspective of someone perusing their job listings it's very easy to think of them as "a tech company." But what they're ultimately selling is access to their content.