Good question!
I was flying to Santorini with Ryanair 3 weeks ago, so dropped my case off in Departures B, but the security area was closed and we were directed upstairs to Departures A security which was rammed with about 5/6 lanes open but through in 15-20 mins.
Only Ryanair use Departures B so in theory, this should be open for these passengers, can only assume there’s not enough security staff for both sets of departure areas…