Last Sunday, I've asked two questions, one on Home Improvement and one on Community Building. Yesterday, I've also answered a question on Role-Playing Games. As far as I know, those were my first posts on said sites. (I could be mistaken and have posted a now-deleted post, but on three sites, that's rather unlikely.)
I was curious how they have been reviewed. However, looking at the timeline of each of these posts, I can't find an entry for a First Posts review. It's not that these are hidden for you as author of the post, since I do see them for my first posts on Stack Overflow and Ask Different. The First Posts review queues on those sites are empty now (even when opened from a private window), and meanwhile there have been other first posts reviewed on at least the DIY and RPG sites.
So I assume the review tasks weren't generated in the first place. My question is: why? I did already have some contribution on those sites in the form of suggested edits. According to @Taryn, that shouldn't matter:
If it's their first post, then it is eligible for review.
I have 'created' tag wiki excerpts on all three sites (the Community Building one is now orphaned) - would that be the cause? In those cases (example) the Community user is listed as the creator of the first (empty) revision.