I think you simplified and misunderstood. The program is the tool. You can't not learn it. But learning to swing hammer is not the same as learning to build house. But you don't learn to build a house by having carpenter show you one tool at a time and telling you what it does. You learn by seeing the problems that exist…
In my experience, not at all. At my company only a handful of our artists (40~ member team) can use SD at an expert level. It's somewhat rare that we even need to apply that knowledge to our projects. It doesn't detract from our work nor is it a pre-req for being hired. More of a nice addition to someone's skill set.…