Gen 4/Diamond - Injected wondercards do not activate gift flag

[glencoe2004]

Describe the bug
In Pokemon Diamond (and possibly other Gen 4 games, I haven't tried them yet), PKHeX does not set a "Gift Active" flag when injecting wondercards, thus causing injected wondercards to not be collectable from the deliveryman.

To Reproduce
Steps to reproduce the behavior:

1. Open a Diamond savefile in PKHeX
2. Inject wondercard
3. Go to pokemart and observe that there is no delivery man

Also, I've found a program that seems to be able to set the flag: https://projectpokemon.org/home/forums/topic/5870-pok%C3%A9mon-mystery-gift-editor-v143-now-with-bw-support/page/12/#comment-99506

To use it, load the save file, then on the left side of the program click on the "Gift Active (D/P only)" checkbox

I've attached two saves, one from before "treatment" and one after, to help in debugging:
Saves.zip

Expected behavior
The flag should be set correctly, so the gift can be received from the deliveryman

Screenshots
If applicable, add screenshots to help explain your problem.

Additional context
Add any other context about the problem here.

[Lusamine]

I was able to get the delivery guy to show up by injecting both the PCD and PGT, but not either separately.

This seems to be a change in behavior. The comments on this guide on Project Pokemon show that it used to work with just the PGT. There are a lot of questions about why he doesn't appear, and one of the comments suggests injecting both. I'm guessing this wasn't reported for a long time because the workaround existed.