The final trim pass changes the artifact after validation, so I would validate the returned script again. A sentence cut to meet the word budget can lose a negation, a required transition, or the referent needed by the next scene while still having the right JSON shape.

For pacing, word count is a useful early budget, but the selected voice’s synthesized duration is the closer test. Numbers, abbreviations and punctuation can make equal word counts speak differently. A short pilot render could catch those cases before the episode enters the unattended production stages.