Why can some PKCS#8 private keys be imported and some can not?

Question

I have been trying to import my PKCS#8 private key from Apple (used for signing JWTs for their Web services/APIs), for use with the browser's Subtle Crypto API (https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/importKey#pkcs_8_import). When I try with my private key it fails saying "Data provided to an operation does not meet requirements" but when I use the private key used in the example, it works. The code I have been trying with is from the example on the above URL.

I need a solution that works with vanilla JS, so I can't use npm packages.

The code I use for importing is this:

async function getPrivateKey() {
  try {
    const privateKey = await importPrivateKey(failingPemEncodedKey);
    //const privateKey = await importPrivateKey(succeedingPemEncodedKey);
    console.log('privateKey', privateKey);
  } catch (error) {
    console.log('ERROR', error.message);
  }
  return privateKey;
}

const failingPemEncodedKey = `-----BEGIN PRIVATE KEY-----
MIGTAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBHkwdwIBAQQg/zwtY1nn6uLpYyukIMgEX4pNgp7GQFevZSr9jkMFSR6gCgYIKoZIzj0DAQehRANCAASC0fq/OiBuA2UpHukZHxj88cZJXoesjhxBfO/XAKGlnRFM0QomoF1aoFlkFGvHU/3h53J/dxAwRzNSy++6CyEu
-----END PRIVATE KEY-----`;

const succeedingPemEncodedKey = `-----BEGIN PRIVATE KEY-----
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
-----END PRIVATE KEY-----`;

async function importPrivateKey(pem) {
  const pemHeader = '-----BEGIN PRIVATE KEY-----';
  const pemFooter = '-----END PRIVATE KEY-----';
  const pemContents = pem.substring(
    pemHeader.length,
    pem.length - pemFooter.length
  );
  const binaryDerString = window.atob(pemContents);
  const binaryDer = str2ab(binaryDerString);
  const privateKey = await window.crypto.subtle.importKey(
    'pkcs8',
    binaryDer,
    {
      name: 'RSA-PSS',
      hash: 'SHA-256',
    },
    true,
    ['sign']
  );
  return privateKey;
}

I have tried the code in a StackBlitz but it is the same result. Does it make sense to someone, that can explain what I am doing wrong? https://stackblitz.com/edit/js-kg244r?file=index.js