merge PDF/A files. or manipulate them

I am using pdf-lib npm package to merge multiple PDF files. but when i try to merge PDF/A files i recieve the following error

error

code snippet

import { PDFDocument } from "pdf-lib";

/**
 * Merge multiple PDFs provided as an array of Buffers.
 * @param pdfBuffers Array of Buffers where each Buffer is a PDF file to be merged.
 * @returns A Promise that resolves with a Buffer of the merged PDF.
 */
export async function mergePdfs(pdfBuffers: Buffer[]): Promise<Buffer> {
  const mergedPdf = await PDFDocument.create();

  for (const pdfBuffer of pdfBuffers) {
    const pdfDoc = await PDFDocument.load(pdfBuffer, {
      ignoreEncryption: true,
    });

    const copiedPages = await mergedPdf.copyPages(
      pdfDoc,
      pdfDoc.getPageIndices(),
    );
    copiedPages.forEach((page) => mergedPdf.addPage(page));
  }

  const mergedPdfBytes = await mergedPdf.save();
  return Buffer.from(mergedPdfBytes);
}

i read PDF/A wiki, PDF/A conformance states that JS and executable file launches are forbidden.
but all these websites like smallPdf and I<3PDF seem to still be able to do it.