Its not inexplicable at all, as I and oters have already explained in detail, and you chose not to reply to.
You complain about having to correct oversteer in PC2 and the movement of the wheel back and forth to balance on the edge of slip (and that is what you are taking issue with here, the small opposite lock corrections and steering corrections being applied) and single out times when it occurs in PC2, yet have ignored the times when its occurring in AC, often at the same corners and near as damn it the same time.
Here it is in PC2:
View attachment 696121
And here in AC:
View attachment 696122
If you watch back the video from 1:06 to around 1:17 in x0.25 replay speed (youtube settings will let you do this) the degree of 'hunting' for the slip limit and oversteer correction is near as damn it identical in both.
You also seem unaware that this is exactly what happens in reality:
Insults in place of a reasoned point, not a great way to go at all.
I've tried PC2 on a PC, its almost indistinguishable from my PS4 Pro.
The handling is not badly programmed, and so far you have failed to show otherwise.
You don't like it, that however is quite different to it being bad or unrealistic. Now my apologies if it comes across the wrong way, but so far we have been told that four cars are 'undrivable' in PC2 because they are so wrong and PC2 is so 'rubbish'. Yet in every case numerous members have driven them and found them to be not only drivable, but that they react very realistically and in comparison to AC, very similar to it.
The cars in question have been the M3 E30 Grp A, Enzo, '66 Mustang and GT3 RS.
The GT3 I have already covered, the rest....
...so you can see that to date these claims have been rather baseless.
Now to reiterate a few questions you didn't answer in the other thread, how do you have your wheel configured in PC2?