StonecutterInventory#setResult(ItemStack) is ignored in PlayerStonecutterRecipeSelectEvent

Expected behavior

Since the PlayerStonecutterRecipeSelectEvent has a getStonecutterInventory method that returns a StonecutterInventory instance which has a setResult(ItemStack) method, I expect the result to be correctly set.

Observed/Actual behavior

The result is not set.

Steps/models to reproduce

Create a simple plugin with the PlayerStonecutterRecipeSelectEvent in use like this:

@EventHandler
public void onStoneCutter(PlayerStonecutterRecipeSelectEvent event) {
    StonecutterInventory inventory = event.getStonecutterInventory();
    StonecuttingRecipe recipe = event.getStonecuttingRecipe();
    ItemStack result = recipe.getResult();
    ItemStack newResult = result.withType(Material.BARRIER);
    inventory.setResult(newResult);
}

Notice that the result does not change.

Plugin and Datapack List

Just the plugin I am currently making, no datapacks.

Paper version

This server is running Paper version 1.21.5-101-main@a033e3b (2025-05-25T07:31:15Z) (Implementing API version 1.21.5-R0.1-SNAPSHOT)
You are running the latest version
Previous version: 1.21.5-94-b70bca6 (MC: 1.21.5)

Other

No response

Start at PlayerStonecutterRecipeSelectEvent and the StonecutterInventory#setResult(ItemStack) path, then reproduce the behavior with the plugin example against the stated Paper version. Trace how the selected recipe result is applied and verify that changing the inventory result changes the stonecutter output.