"If the combat is occurring in a convoy sea zone containing transports
owned by the defender, they may not be taken as casualties until no
more escorting sea or air units remain in the combat. "
If attacker has submarines remaining but convoy escorts are down to only fighters the submarines would seem to stop firing until the defending fighters are destroyed at which point submarines can roll attacks against any remaining convoy targets.
This is inconsistent with previous rules regarding submarine hits to transports if there are no other legal targets:
“and hits can be assigned to transports only if there are no other eligible units.”
Axis & Allies Europe 1940 2nd Edition
Please confirm if I’m reading the rules correctly and if any insight into why the change