It's a cut-off
SIAll.
It's a cut-off! If you're so tight time on time you're questioning whether it's Sched ETD or actual you're much better off not wasting any more time and going to a Customer Service desk and seeing what they can do for you.
I should think that although sophisticated, it ain't that sophisticated and will rely on the Sched ETD. In fact I've been told that it's actually a 37 minute cut-off but remember you're dealing with 'security' here and they'll have no leeway if your boarding card doesn't swipe green.
S