shouldn't it be?
public List doHarvestOperation(World world, BlockPos pos, IBlockState blockState) {
NonNullList stacks = NonNullList.create();
if (Config.hempHarvestBothBlocks) {
blockState.getBlock().getDrops(stacks, world, new BlockPos(pos.getX(), pos.getY() + 1, pos.getZ()), blockState, 0);
blockState.getBlock().getDrops(stacks, world, pos, blockState, 0);
world.setBlockToAir(new BlockPos(pos.getX(), pos.getY() + 1, pos.getZ()));
world.setBlockToAir(pos);
} else {
# blockState.getBlock().getDrops(stacks, world, new BlockPos(pos.getX(), pos.getY() + 1, pos.getZ()), blockState, 0);
world.setBlockToAir(new BlockPos(pos.getX(), pos.getY() + 1, pos.getZ()));
}
return stacks;
}

1. A bit too late, I already push the new version out.
2. If you want to change anything regarding codes, please do pull requests instead.
3. I know what I am doing, it does really matter to be honest.
   https://github.com/Jacky1356400/IntegrationForegoing/blob/8707160e56a56542da10364694df9cb0cb99fd23/src/main/java/me/jacky1356400/integrationforegoing/handler/plant/immersiveengineering/CropHempPlantRecollectable.java#L32-L33
   Yes, I can get the drop of the top block instead, but again, it doesn't matter.