The car will self correct.[ readapt]
The car has the ability to change its working specs for engine management according to how the car runs...it tries to keep the car in perfect tune if something is a little out of wack and can also change settings according to enginer wear , driving style, etc. That's what makes these so cool.
If a car is running with a slow sensor or a dripping injector ,or whatever- etc, it corrects the management...it does not correct the part. It does not correct the fault, It works around the failing or weakened part..it ADAPTS to that condition... and if the condition is too far out or the part is too worn, it gets to its LIMITATIONS and CAN NOT CORRECT anymore. So, that's where you come to the rescue ...you change some parts and fix some system failures [ that the codes indicate to you] and then the Modules re-adajust to the new parts and repairs.........but it does not know that you put some new parts and repaired some poor conditions until you start it up and go for a ride or two...then it can see that you did some changes by reading some sensors .. get it ???
So, that re-adjustment takes drive cycles to get it where it wants it to be to attain the most effiecientcy. [ IT ADAPTS to the new parts/condition]
But , if you go in there and clear out the old wacked out of spec memory, it goes to BASE Mean [ Zero adaptations] , which should be closer to Factory settings than it was when it was wacked out from the poor running condition caused by a fault/part .
This memory has to stay fit b/c it is tailored to that car and that driver...if it is erased, it has to start all over again...
So, if one makes some out of limit code repairs and wants the car to get back to a close to normal state, dump the old memory and start new..that's all... you don;t want that those old setting running your new parts...it will still have to adapt to the new parts/conditions, but it should be closer and improve as you drive it. .. this is just a recommended short cut to save the drive cycle time it would take for re-adaptation to the new conditions [ which should now be GOOD if you repaired the right stuff]
As I said , if they were way out , they can take a little time to self correct , and in that time, they can still pop codes . So most guys clear the memory to get the thing close to normal right after you do the repairs and you don't have to worry about false codes while waiting for self correct via drive cycles.
You do not have to do this ..it is fully capable of self correction all by itself [ which was one of your questions]...but you have that option to manually do it right away, so that is most guys choice.
Don't expect to change a part, start the car for 30 seconds and wonder why it still has an old code re-appearing. Some guys don't even wait long enough for the car to go into closed loop....
But on the other hand [ and your question], if you repair. for example, a vac leak a while back , the car has already adjusted for the new No Leak condition b.c the car has had a few drive cycles. The memory clear I mention is used/done directly after a repair is made so you do not have to wait for the drive cycles. And it is specially effective if one has repaired an Out of Limit problem code.