No there is nothing gained from adding short and long together.
20-30 MAP KPA would be funney since it mostly decel and low RPM range and sometimes fuel learn is off or on or just having switched from one to the other.
You'll gain nothing by doing all this since PCM is not perfect and many different driving conditions such as going down a hill from full to partly decel so numbers will never be perfect but again as long as trims rotate a bit lean and rich from zero assures O2s can also ramp up and down crossing 0.450 mVolts

If always a perfect zero then O2s would stay constant and that would confuse PCM.

Oh, I wasn't looking for performance but I wantend to understand how this part of the PCM works.
Since I loaded the new IFR curve (considering LT and ST) and resetted the PCM most LTFT are = 0 and only few are +/- 2%. STFT are most of the time +/- 3/5%.
This for different driving conditions (accel/decel) and outside temperatures (40/70F).
When I only considered LTFT, driving style and temperatures had a bigger influence.
But it's clear: as long it runs in closed loop it doesn't make a difference: the O2's will manage that

Yep as long as the trims fit within the STFT operating window tune is fine and long term changes then are just clean up to the PCM over time