Certificate request subject commonName domain is not taken into account

RFC8555 tells:

   The CSR MUST indicate the exact same
   set of requested identifiers as the initial newOrder request.
   Identifiers of type "dns" MUST appear either in the commonName
   portion of the requested subject name or in an extensionRequest
   attribute [RFC2985] requesting a subjectAltName extension, or both.

When the subject of the CSR has CN=abc.dom.org and the subjectAltName has only DNS:xyz.dom.org, by the RFC an order must be created with both abc.dom.org and xyz.dom.org as identifiers. After making the order ready, the submitted CSR is not accepted with the following error:

{
   "type": "urn:ietf:params:acme:error:unauthorized",
   "detail": "Order includes different number of DNSnames identifiers than CSR specifies",
   "status": 403
}

For reference see:
https://community.letsencrypt.org/t/the-way-domain-name-in-the-subject-of-the-certificate-request-treated/116107

No files or tests are named. Start by tracing the ACME CSR identifier validation and reproduce an order containing CN=abc.dom.org with SAN DNS:xyz.dom.org. Done means a CSR whose DNS identifiers are represented across the commonName and subjectAltName is accepted when it matches the order, with regression coverage for this case.