I seem to have come across a little too harsh, apologies IfIg.
The problem being solved by feeding segregation is not the one of fuel contamination.
If you uplift fuel contaminated beyond what is acceptable for the engine to run, you wouldn't start up or alternatively, you have mud in all your tanks and are doomed anyway.
What is avoided is CTR TK contamination in most critical phase of flight. If your CTR TK is carrying problems, (water, other contaminants, low level) you do not want these to be propagated simultaneously into the engines during takeoff. Solved on A320. Yet, sooner or later the CTR TK fuel is introduced into the system anyhow, just not for takeoff.
On the 321 in order to have fuel in CTR, the wing tanks must also full to begin with. Given the pipe connection, the same result is achieved as for A320 without a need to separate the CTR tank. Because only small stream of CTR TK fuel is uplifted at the jet pump into a stream of WING TK fuel, which is then together reintroduced into the approx. 6 tonnes that are now carried at the fuel WING TK and being pumped up to the engines. So the rate of WING TK fuel decay due to CTR TK fuel problem is very small.
True, after some time the mixture in WING TK will reach highes content of CTR TK fuel, approx 50:50 but this will come only after 3 t are consumed by the engine so that 3 t form CTR TK found their way to each onside WING TK. About 2 hours into a flight, I woud suppose, you are running on the richest CTR TK fuel mixture at cruise level.
Compare this to the A320, when after slat retraction (3 minutes, 5000 ft AGL) you are running on 100% CTR TK.
Now, thinking about the take-off part, my guess is that the rate of decay due to CTR TK fuel put up into WING TK is geniously negligable. In fact, is by desing no grater than the fuel flow. Even at TKOF THR FF (which I strongly doubt jet pumps are able to compensate by uplifting CTR TK fuel into WING TK) of let's say 4000 kg/h per engine, in all five minutes only 300 kgs of CTR TK fuel will be transferred in the 6 tonnes originally carried.
FD.