Single dark oak and pale oak saplings accept bone meal despite not being able to grow

Can confirm in 1.18.2.

Can confirm in 22w18a. Here's a code analysis of this issue.

Code Analysis:

The following is based on a decompiled version of Minecraft 1.18.2 using MCP-Reborn.

net.minecraft.world.level.block.SaplingBlock.java

public class SaplingBlock extends BushBlock implements BonemealableBlock {
   ...
   public boolean isValidBonemealTarget(BlockGetter $bg, BlockPos $bp, BlockState $bs, boolean $b) {
      return true;
   }
   ...

If we look at the above class, we can see that the isValidBonemealTarget() boolean always returns "turn" for saplings regardless of any circumstances. No checks are carried out to see what the type of the sapling is, nor its arrangement, resulting in this issue occurring.