That’s not correct.
Following additional allegations in 2012 Starmer asked his Principal Legal Advisor to review the decision to not prosecute in 2009. He didn’t introduce a new role.
He did indeed then propose new processes to avoid a further repeat.
There is no evidence to suggest he was involved in the decision to not prosecute in 2009. His problem here is that he goes around telling people how he was involved in prosecuting x, y and z but then denies having a clue about this. He’s likely guilty of inflating his involvement in x, y, and z.
From what I've read Alison Levitt was already being tasked with looking out for systematic issues, and this came to him, and then he asked her to review the decision.
As you say there was no evidence that anything came to him in 2009. He must have been doing something, as the OP suggested, so is it not likely that he was heavily involved in some cases that were flagged up as priorities? (I'm guessing your first x, y, and z and different cases to your second x, y and z?)