I don't believe it's due to the different scoring modes:
My kills on the Expanded stat's shows 74 kills, 21 deaths.
My kills on "Pilot score" shows 72 kills (total) and 26 deaths (5 bail, 1 ditch, 3 capture, 17 death) plus 1 disco that seems to "not count".
I've only killed 1 ground vehicle (M16) total for the TOD.
On the Expanded stats I (seem to be!) missing the 5 deaths at least (6 if you were to count the one disco as a death, too).
And yet at the same time, I have 2 more kills accounted for in Expanded stats than I do in score - which just doesn't make much sense...