The old ladder measured how much you produced. The new one measures whether you were right, and how you knew. That one change is the whole answer, and everything else is consequence.
Evidence at each level
These map to the four levels in the Product Builder job ladder. The JDs describe the scope; this is the evidence a calibration room should read.
At L4, the loop works in your hands: one surface shipped, a metric you can name, an eval you wrote before you built. At L5, you set a bar others inherit: your rubric became the team's, your prototype-first habit changed how the builders next to you work. At L6, you were trusted with a bet that was expensive to reverse and it paid off, with the reasoning on record from before you knew. At Principal, you set the standard the pillar is judged against and your reasoning is quoted by people who do not report to you.
Every level leans on the same load-bearing thing: a decision made under uncertainty with the reasoning available to check. That is hard to grade on purpose, because it is hard to fake. You can pad a document. You cannot pad a metric that did not move.
The real constraint
It is not the rubric. It is the reviewer. Most product orgs have calibration rooms full of people who learned to grade documents, and grading a bet requires knowing enough to separate judgment from luck. If your reviewers can only read a PRD, you will keep promoting the best document producers into a role where documents no longer exist. Rewrite the evidence column of your rubric before the next cycle, then make sure the room can read the new column. And if you are an IC, start a decision log today: one bet, the reasoning, what you expect. In six months it is the one piece of evidence the new ladder is built to read, and almost nobody else will have it.