Telling you what happened here...
1) Did it the authentic way with Diamond to get Entei. Showed pre-event info.
2) Did the event. Post-event info came up.
[Good so far.]
3) On my HG, PokéGen'd the event Raikou, Suicune, and Celebi WCs. Obtained, boxed, and saved.
4) Back to the PC, two instances of PokéGen: one for HG, the other Black. Dragged over the three WC PKMN to the Black boxes, changed the place to the post-event tag for the dogs, left Celebi alone.
5) On to Black, couldn't trigger the Zorua event. Found out that the event trigger wasn't set. I set it to pre-event, triggered, caught, saved.
6) Back to PokéGen I go, I see that all the dogs and Celebi had the post-event trigger set.
[Again, we're all good, right? Wrong!]
7) Reloaded the save after an inventory edit, and I get hyphened dash across where I encountered it. This is where it normally tells you about the event, so...
8) Back to PG... it STILL says "Post-Event".
Some help here? Thanks.