To put it together Flap3 does save fuel. The pros and cons for steep approach
1. In A320 Flap3 landing is not an issue because Flap3 is mandatory for abnormal landings.
2. Landing distance is not an issue as Flap3 takes appx.150mtrs extra. Also the reference WT is MLW which may not be the case mostly.
4. From stabilization point of view only the ground speed can be limiting because in turn it will breach ROD criteria.
5. This should only come in play with tailwind which also the most penalizing for landing distance.
For stabilization tailwind may have to be avoided and opposite runway can be chosen if possible. Off course fuel saving can be done on another day.