Seems to be a bit of confusion…
Reading About the Project Showcase category it seems to be the other way around, at least according to that post. It says explicitly “This is a place for devs to post their new/unreviewed projects”. And “This category is the only section in which you as a developer are allowed to promote your own projects”.
The way I read it is that if I’m a developer of a software that’s not ( yet 
) recommended by Privacy Guides, “Project Showcase” is the only appropriate place, and that requires membership in the developers group… So, it makes no sense to require membership in developers if that group is only for recommended developers, if the group is the only place to showcase software that’s not recommended!
Or am I completely misreading this?