Player heads should have a config option to drop outside the grave. This is mostly applicable to a pvp environment where you'd like the deceased player's inventory to be safe from the attacker and griefing, but the player head is a still accessible as a pvp reward.

It already is :D
It's in the config under inventoryConfig->dropPlayerHead

oh, upon further testing I realized that by "drop", I mean I want the player head to drop outside the grave and not in it. Is that a feature that I'm missing, or is not possible with YIGD. I've removed any other mods or datapack that deal with player heads and it doesn't seem to make a difference.

The very second line, too! Thanks --I really don't know how I missed that.

Closest thing you would get is to add minecraft:player_head to the data/yigd/tags/item/grave_incompatible.json tag with a datapack. This would result in all player heads dropping, including the ones kept in your inventory when killed.
If you want it improved, let me know and I'll reopen the issue (unless you can do it yourself. I'm not really sure weather or not that's something only I can do or not. You can still let me know anyway).
Let me know if there's anything you need help with, or if something is still unclear

Thanks, I'll try that out and let you know!