<<Two-factor authentication. You must turn off two-factor authentication for your Apple Developer ID to publish with Thunkable. Please click here to see our recommendations for turning off two-factor authentication>>
Just found the line you were referring to in the Troubleshooting section. Have updated the docs to remove it, but the same page does also state:
Since Two Factor Authentication (2FA) is now the default for Apple accounts, it is assumed that you have this enabled,
and
Two-factor authentication helps to keep your account secure and Apple has made it mandatory for new developers to turn two-factor authentication on. If you do have 2FA turned on, you’ll need to complete the following steps to confirm your identity with Apple.