Carrion Grub gets additive bonuses to power [Can’t reproduce]
It reads „At the begnning of the combat on your turn: This creature's power becomes X, X is equal to the greatest power among creature cards in your graveyard“. Instead, it receives +X, increasing in power each turn.
A similar situation, I believe, happens with Nighthawk Scavenger — instead of „its power becomes X“, it receives +X to power.
Android 10, Samsung Note 9