I don't think June would be last, but I think what they have done, is fast forwarded into the June/July pool and started cherry-picking the cases, like GuyanaGirl's where there is 10 years of relations -- very low risk, and probably paid very little attention. They will eventually start working on them in parallel with the April - June pool.
Ultimately, the goal is to reduce the "backlog" to the manageable 12 month wait. Given my predictions (adding 13.5mos to date of receipt), they would not be able to clear out the backlog, and continue to process at their current rates, without "weeding out" the easy cases up ahead. Dealing with PCC's, missing or requested docs, interviews, etc from the current active pool slows them down. The fast forward is a bit of a means to offset that.
Again, just an "educated" guess as to what is going on...