From what I understand about endorsements, you cannot actually use an endorsement policy with an AND condition in BYFN. You can do that only when you create your own client using one of the SDKs.
What happens here internally is that the BYFN script leverages the peer CLI to run invokes on processes. The problem is that peer CLI cannot collect multiple endorsements. Therefore, AND has no use here as only one endorsement will be collected. Validation fails hence.