Crafting bamboo hanging signs gives 2 items instead of 6

The Bug

When crafting bamboo hanging signs it results in 2 items instead of 6 like the other hanging signs

Reproduce

• Get some planks and bamboo planks
• Place a crafting table
• Right click on the hanging signs
• Click on the bamboo hanging sign recipe

Observed Result

It only crafts 2 hanging signs

Expected Result

It would craft 6 like the other signs