For an experienced developer, that would be a workplace project, which you probably could not see. Indeed, it _should_ be a workplace project; would you hire a professional developer whose best work is their personal project?

But if what you're saying is that the mark of an ideal developer is one who has produced a personal-time product of professional quality, where every checkin is to workplace standards, and has developed the project from conception all the way to release, again all on personal time, then what you're asking for is not a developer who also codes as a hobby, but a developer who (at least part of the time) works two actual jobs. One of which they do for free for portfolio development. I don't find that to be a reasonable expectation, even if it would give employers "important insights".