Why did rerunning a migration multiply already converted values again?

import {DatabaseSync} from 'node:sqlite';
import {TextDecoder} from 'node:util';
import {inflateSync} from 'node:zlib';
import {posix} from 'node:path';
import {createHash} from 'node:crypto';
const rows=(db,sql)=>db.prepare(sql).all().map(r=>({...r}));
const failed=(action)=>{try{action();return null;}catch(e){return {code:e.errcode??e.code??e.name};}};

import assert from 'node:assert/strict';
const run=function run(i,corrected=true){
    const db=new DatabaseSync(':memory:');try{db.exec('CREATE TABLE target(id TEXT PRIMARY KEY,size INTEGER,version TEXT);');
      const add=r=>db.prepare('INSERT INTO target VALUES(?,?,?)').run(r.id,r.size,r.version);for(const r of i.initial)add(r);let error=null;
      for(let n=0;n<i.runs;n++){db.exec('BEGIN;');if(corrected&&db.prepare("SELECT COUNT(*) AS n FROM target WHERE version IS NULL OR version NOT IN('old','new')").get().n){error='incompatible-version';db.exec('ROLLBACK;');break;}
        db.exec("UPDATE target SET size=size*10,version='new'"+(corrected?" WHERE version='old'":''));db.exec('COMMIT;');if(n===0)for(const r of i.later)add(r);}
      return {error,records:rows(db,'SELECT * FROM target ORDER BY id')};
    }finally{db.close();}
  };
const cases=[{"label":"misleading base","input":{"runs":2,"initial":[{"id":"A","size":2,"version":"old"}],"later":[]},"expected":{"error":null,"records":[{"id":"A","size":200,"version":"new"}]},"corrected":false},{"label":"corrected base","input":{"runs":2,"initial":[{"id":"A","size":2,"version":"old"}],"later":[]},"expected":{"error":null,"records":[{"id":"A","size":20,"version":"new"}]},"corrected":true},{"label":"later old-version row converts once","input":{"runs":2,"initial":[{"id":"A","size":2,"version":"old"}],"later":[{"id":"B","size":3,"version":"old"}]},"expected":{"error":null,"records":[{"id":"A","size":20,"version":"new"},{"id":"B","size":30,"version":"new"}]},"corrected":true},{"label":"incompatible source version held","input":{"runs":1,"initial":[{"id":"A","size":2,"version":"other"}],"later":[]},"expected":{"error":"incompatible-version","records":[{"id":"A","size":2,"version":"other"}]},"corrected":true},{"label":"missing representation version held","input":{"runs":1,"initial":[{"id":"A","size":2,"version":null}],"later":[]},"expected":{"error":"incompatible-version","records":[{"id":"A","size":2,"version":null}]},"corrected":true}];
for(const test of cases){
  const actual=run(test.input,test.corrected);
  assert.deepEqual(actual,test.expected,test.label);
  console.log(test.label,actual);
}