There is an entire universe worth of knowledge in the security space that has nothing to do with software development. I'd agree that 98% of the security world is "bullshit", but one of the reasons every company has such awful security is specifically because too many people think "software development" == "security", and this narrow mindedness means they end up failing to accomplish any of the security pillars that have nothing to do with software development.
There is a lot of overlap specifically with secure development and software development, but saying "software development and security are basically the same thing" is naive. I like to compare it to a company's legal team: if you're going to court over a technical topic, you definitely want some people on your legal team that have software experience and you definitely want your general counsel to be technically educated, but that doesn't mean you're just going to take a software developer and make them your general counsel. You still need an actual lawyer, because there is an entire universe of law-related knowledge that you need that a software developer doesn't know.