To summarize the current situation:
Alliance Perk L3: Soldier Exchange Program (+3 alliance gait capacity)
* Works on offense (i.e. we can receive +3 extra troops for attacks)
* Does NOT work on defense (i.e., donations to our town centers are 3 less than they should be)
Sally Ride's Alliance Gate Troop Capacity:
* Works on offense and defense
Sally Ride is mentioned because it did not work on defense when introduced; was fixed for awhile; then stopped working when the missing +3 alliance gate bug was introduced; but Sally works now.