In some respects this is clearly an ideal way to find a job, in the sense that on average it's going to achieve a much better fit than random software engineers

In some respects this is clearly an ideal way to find a job, in the sense that on average it's going to achieve a much better fit than random software engineers applying to random "Software Engineer I/II/III" positions. And have literally gotten a job or two this way, more or less. But I think there are a lot of practical issues. This is extremely resource intensive (in terms of time and emotional investment) modus operandi. And considering that an explicit part of the process you describe is promoting yourself for jobs where the company isn't even actively hiring, you're going to have to try this with a lot of companies. Most companies are pretty opaque and many don't even know what they need, and it's certainly even rarer for them to randomly drop crucial "oh man, wish we could find a good database guy who also practices Wing Chun kung fu for our dojo" hints by word of mouth. It's like finding love, almost. It's great when this sort of serendipity happens and folks can maximize the chance of it happening by absolutely networking the hell out of themselves but I don't think it's something you can rely on.