Since March 19th, the number of reviewable "First Posts" has declined considerably. At first I suspected a yet-to-be-announced feature change in the review system, e.g. "First Posts" that receive votes or comments after a few minutes won't show up in the review queue anymore (i.e., are considered "reviewed" implicitly). However, the question Asana Math + XeLaTeX: missing math upon resaving or editing in Adobe Acrobat Pro didn't show up for review for 20 minutes (after which it received a comment), and doesn't show up right now. Taking a second look at the Review history, every "First Post" reviewed after March 19th, 18:00 GMT (20 so far) has been an answer -- it seems "First" questions simply don't show up in the review queue at all.
So: Is the "First Posts" review queue partially broken?