I've just found the Oliveira judgement for his sentencing appeal
http://www.saflii.org/za/cases/ZASCA/1993/62.html
His sentence was reduced to 9 years on appeal, but I do see quite a difference between his and Pistorius' cases.
As far as the courts rejecting that either of them had a valid defence of PPD, the cases are the same. However, in Oliveira's case there was no question that he thought the men outside were strangers/intruders on his driveway, he saw them and didn't recognise them. So there was an overreaction and while there was intent to harm them, there was nothing dishonest or to raise suspicion about his evidence, that he was hiding a reason for taking his gun and shooting.
In Pistorius' case, I have to say that if Masipa had drawn the correct legal inference during the trial, and concluded that he was not in genuine fear for his life and not acting in private defence, there was a much bigger inference to be drawn from this, an irresistible inference which would have required her to revisit the State's main charge and reject his version as a fabrication. This alternative version/charge/motive was absent from Oliveira's case.
I believe that without a genuine justification for shooting the perceived intruder he should be sentenced on the grounds that he is an unconfessed murderer, and he has gone to exceptional lengths to deceive the court and avoid responsibility.
That is my personal view, that he has so far not explained to anyone what happened, so the courts should not have mercy. I don't think Oliveira is comparable in that respect.