When breaking/placing a medium Amethyst Bud the sound of the large one is played and vice-versa. This isn't very noticeable in vanilla gameplay since the sounds are very similar (the same?). But this does affect custom resource packs.
Here's a code snippet from net.minecraft.world.level.block.Blocks
:
public static final Block LARGE_AMETHYST_BUD = register("large_amethyst_bud", new AmethystClusterBlock(5, 3, BlockBehaviour.Properties.copy(AMETHYST_CLUSTER).sound(SoundType.MEDIUM_AMETHYST_BUD).lightLevel((state) -> 4)));
public static final Block MEDIUM_AMETHYST_BUD = register("medium_amethyst_bud", new AmethystClusterBlock(4, 3, BlockBehaviour.Properties.copy(AMETHYST_CLUSTER).sound(SoundType.LARGE_AMETHYST_BUD).lightLevel((state) -> 2)));
Confirmed.