Yes, I think so. I have been on some European flights recently where the cockpit door has been open for at least a moment, including one not unadjacent to here.

On our EZ NCE-LTN, delayed because LTN was closed, the captain came into the cabin several times, using the cabin crew's handset to keep us up to date with what was (or wasn't) happening.

In the case of LiarAir, I guess the main door was kept closed just in case they needed to be ready to fly quickly, hence no risk of attack from outside.