It's certainly true that many General Counsel positions aren't openly advertised. When I recruited my successor to my most recent GC role I tapped into my network and found a highly suitable person to replace me. To increase diversity at senior in-house level, it would be helpful if recruitment were open. Maybe a website specifically to advertise GC positions?

Until something like that happens, the advice in this article is definitely worth following if you're hunting for such a role.