I have a fix for this if anyone is interested. It doesn't even require scripting.
1. Create a combo with a grave tile and none type.
2. Immediately after it in the combo page, create a combo with grave tile and grave type.
3. Replace the pushable combo in the graveyard with the first one above.
4. Place 2 Block Hole (Block->Next) flags: one above the pushable grave, and one below it.
5. Enjoy success!
EDIT: To be NES-compatible, use this new None-type grave combo as the combo on the upper left screen of the graveyard, the 2nd grave on the 2nd row, and also on the upper right screen of the graveyard, but the 3rd grave on the 2nd row. Both quests have those same 2 graves with no ghinis coming out of them until after it has been pushed, but of course only one is pushable in each quest. The trick above needs only to be done in each quest once, at the pushable grave.