Espruino on your watch!

Because it takes 1 as 1 second? Try higher values. Anyway the manual mode may be safer. What about something like this

  E.enableWatchdog(5, false);
  setInterval(() => {
    if (!BTN1.read()) {
      E.kickWatchdog();
    }
  }, 1000);

That should reboot if you hold button for >5 seconds. Which actually may not be best idea if this can happen normally but one can perhaps combine it also when being on charger (D2.read()).