You cannot convert blocks into dirt paths when non-full blocks are above them

The Bug:

You cannot convert blocks into dirt paths when non-full blocks are above them.

Steps to Reproduce:

1. Build the setup as shown in the attachment below. 

1. Obtain a shovel and attempt to turn all of the three grass blocks into dirt paths.

2. Take note as to whether or not you can convert blocks into dirt paths when non-full blocks are above them.

Observed Behavior:

You cannot convert blocks into dirt paths when non-full blocks are above them.

Expected Behavior:

You would be able to convert blocks into dirt paths when non-full blocks are above them.

Code Analysis:

Code analysis by @unknown can be found below.

The following is based on a decompiled version of Minecraft 1.18 using MCP-Reborn.

net.minecraft.world.item.ShovelItem.java

public class ShovelItem extends DiggerItem {
   protected static final Map<Block, BlockState> FLATTENABLES = Maps.newHashMap((new Builder()).put(Blocks.GRASS_BLOCK, Blocks.DIRT_PATH.defaultBlockState()).put(Blocks.DIRT, Blocks.DIRT_PATH.defaultBlockState()).put(Blocks.PODZOL, Blocks.DIRT_PATH.defaultBlockState()).put(Blocks.COARSE_DIRT, Blocks.DIRT_PATH.defaultBlockState()).put(Blocks.MYCELIUM, Blocks.DIRT_PATH.defaultBlockState()).put(Blocks.ROOTED_DIRT, Blocks.DIRT_PATH.defaultBlockState()).build());
   ...
   public InteractionResult useOn(UseOnContext $$0) {
      Level level = $$0.getLevel();
      BlockPos blockpos = $$0.getClickedPos();
      BlockState blockstate = level.getBlockState(blockpos);
      if ($$0.getClickedFace() == Direction.DOWN) {
         return InteractionResult.PASS;
      } else {
         Player player = $$0.getPlayer();
         BlockState blockstate1 = FLATTENABLES.get(blockstate.getBlock());
         BlockState blockstate2 = null;
         if (blockstate1 != null && level.getBlockState(blockpos.above()).isAir()) {
            level.playSound(player, blockpos, SoundEvents.SHOVEL_FLATTEN, SoundSource.BLOCKS, 1.0F, 1.0F);
            ...

If we look at the above class, we can see that you can only convert blocks into dirt paths using shovels if air is above them. This is evident through the following line of code:

if (blockstate1 != null && level.getBlockState(blockpos.above()).isAir())