This is WAD.
AI still use the old Armageddon targeting rules (as long as a province in the target zone is in range, all provinces in that zone can be attacked). This is not true for players anymore and only provinces in range can be attacked.
BTW this is fully moddable as all major features in Darkest Hour

misc.txt
# Apply air and naval unit's range limits on missions to Areas and Regions. 0 = Disabled, 1 = Enabled, 2 = Enabled for AI countries too (Not recommended!!!)
1 #0
The "Not recommended" note is because we haven't tested that extensively (this requires many test games with very close observatrion of AI activities) and theoretically this could hurt the AI.