Order fo screenshots is broken. Recently I re-submitted my plugin just to fix the order. I triple checked that the order was correct in the submission form. But that is not being considered in the plugin manager. It seems that they are in alphabetical order but reversed.
I can confirm this. The good thing, however, is that Adobe appears to be aware of this already.
This is a known issue and the team is aware of it. We regret the inconvenience.