Feedback on copy is usually a feeling. A score with the failing lines named is something a writer can act on, and something two people can disagree about productively.
Why score before rewriting
A rewrite with no diagnosis is a different email, not a better one. It might be better. Nobody can tell, and the next email will have the same problems because nothing was learned.
Scoring first means the rewrite is aimed at named failures, and the re-score tells you whether it worked. Over a few rounds the writer stops making the same three mistakes, which is worth more than any individual improved email.
The two checks most rubrics miss
Beyond the standard craft dimensions, two things get checked that scorecards usually skip.
Where it gets used
On a campaign that is underperforming and suspected of a copy problem. On inherited copy nobody has read properly. And as a standing check before a sequence goes live, where it catches the repetition that only shows up when all four touches are read together.
Runs well with
Skills compound. These are the ones we usually install alongside it.