I think it depends on our contribution to this site. This website is a fast growing one. In 2 to 3 months this website crosses 10,000 members mark. Then the posts posted by the members are huge and the moderator is adding more sections to this site. Then obviously they required few editors. Then they will select on contribution basis and supporting to other members or not
You are absolutely correct. When boddunan requires editors, it will ask for open invitations and selects the editors based on the contribution and activeness.
Recently application was invited for editorship. Participation in various activities on the site, writing quality articles and writing helpful comments are the criteria.