Well put, and this harks back to the classic Rich Hickey talk "Simple Made Easy". For Bob the process is easy because he's internalized all the complexity. It's not actually simple. But it's subject to the conflation of "simple" and "easy" that Hickey warned about.
Another way to it has been put is "beginner's mind" or the "curse of knowledge". Once Bob has mastered the many intricate steps it is hard for him to see them clearly and remember the difficulty he himself had. A truly simple process on the other hand would be (relatively) easy for everyone, not just the expert. And of course as you point out it can be difficult for a removed observer to tell the difference.
Another way to it has been put is "beginner's mind" or the "curse of knowledge". Once Bob has mastered the many intricate steps it is hard for him to see them clearly and remember the difficulty he himself had. A truly simple process on the other hand would be (relatively) easy for everyone, not just the expert. And of course as you point out it can be difficult for a removed observer to tell the difference.