The bug
Placing a tripwire hook updates blocks around an opposite facing tripwire hook on the same axis even when they are not connected.
See also Hermitcraft 4 Ep. 96- Wireless Redstone Door! (sorry cub).
How to reproduce
Build a setup as shown in the attached screenshot
Place a tripwire hook on the gold block so that it faces the other tripwire hook
→ You will see that the trapdoor is updated and switches to the closed state
Can confirm for MC 1.12.1.