Duplicate string via tripwire hooks

Using the setup pictured below, and placing a water block where the cursor is pointing drops 4 string and 2 tripwire hooks despite only placing down 2 tripwire hooks and 3 string. I tested this on a Vanilla 1.18.1 server.

This is just two tripwire hooks spaced apart by 3 blocks with 3 string placed down connecting the two hooks.