Minecraft wiki entry for Stonecutter, associated text: Even though the iron blade appears to be spinning rapidly, it deals no damage and has no hitbox.
A stonecutter is more efficient than a crafting table for making stairs, because the crafting table requires 1.5 blocks per stair (six blocks of stone to make four stairs) while the stonecutter requires just one block per stair.
The stonecutter was most likely based on the old Bedrock Edition stonecutter, as it has similar functionality.