Multiplication bundle Glitch

What I expected to happen was:
For it to not work and just be bordem.

What actually happened was:
A multiplication which can go over the stacks.

Steps to Reproduce:
1. Have a crafting table, A bundle and 3 blocks of "Item" like diamonds and redstone worth of items. (For this example I am using diamonds)
2. Set up how you usually do and use the bundle to take a grid worth of items.

3. Shift click the block and it will begin multiplying.

4. put the item back in the open slot and take it out with the bundle again to continue this forever.

But there's a catch:
Once you do this over 26-30 it will change it all to diamond blocks, But I mean they can just uncraft it and do it easily again.
Proof of it going over the stack limit: