Why should a rewrite not get longer?
A rewrite should stay near the length of the draft. Extra sentences add claims that were not there. Plainvoice shows the word-count delta and does not promise a detector will accept the result.
A longer rewrite looks helpful and then smuggles in a reason, a greeting, or a fact the draft never had. The reader cannot tell which sentence was yours.
Plainvoice keeps the rewrite close to the draft and prints the word-count change under the pair. A locked number stays as written. If the draft was 100 words, the rewrite should not become a new essay.
Read the delta before you send the text. If the rewrite grew, cut the sentence that was not in the original.
Style
100 / 400 words. No account. No card.