This image from the faq is confusing me:
It's excluding people who know programming but don't have a career in it. Is this correct?
It's not solely for career software developers, but mainly for them.
The first line of the FAQ reads (my bold):
Programmers - Stack Exchange is for expert programmers who are interested in conceptual questions on software development.
You don't get to be an expert unless you've spent a lot of time doing something and you usually only spend a lot of time doing your job or your passion. We welcome questions from anybody, but we really want the experts to answer them. That way we can "make the internet better" and hopefully software development practices too.
However, what the graphic represents is where the question sits not where the questioner sits. On all Stack Exchange sites the primary elements are the question and answer not the people who post those questions and answers. You vote on posts not people (for example). So if your question is:
What's the best chair?
Then this is off topic as it applies to anyone who works at a desk all day not just software developers.
Equally if your question is:
I have a bad back due to an injury I suffered when I was 10, what's the best chair?
Then this is too localised as the answer is specific to you and you alone.
(Note: these aren't the best example questions as there's no chair question that would be on topic - but you get the idea).