Feynman certainly wasn't a professional programmer and I don't believe he spent much time writing software, but he worked for a while as a consultant to Thinking Machines Corporation and gave a (published, rather good) set of Lectures on Computation.

So if he doesn't sound like a programmer, it may be for reasons other than not being familiar with the insights that come from spending time making software.

(I don't think Feynman had any more difficulty than you in believing that simple rules produce very complex behaviour. I think he was trying to express how most people feel about it.)