showSaveFilePicker: writable.write with position would resulting wierd file

[DeltaLaboratory]

import {
  showSaveFilePicker
} from 'native-file-system-adapter';

let file = await showSaveFilePicker({
  suggestedName: fileMeta.name
});
const writable = await file.createWritable();
let promises = [];
for (let i = 0; i < 10; i++) {
  // recieve some file at buffer 
  promises.push(new Promise(async (r) => {
      await writable.write({
        type: 'write',
        data: buffer,
        position: i * 1024 * 1024 * 100
      });
      r();
    })
  })
}

await Promise.all(promises)
await writable.close();

Browser: Firefox 123.01, Chrome mobile etc -> browsers not supporting showSaveFilePicker natively

will resulting partially written file. it may be impossible to implement this in current fallback but i didnt really read library code so just create issue