I actually found the answer. Took some time, but it is stated here
Under 2c at the Note.
"Smartcard cache entries are created for certificates with a subject name or with a subject key identifier. If the certificate has a subject name, it is stored with an index that is based on the subject name and certificate issuer. If another certificate with the same subject name and certificate issuer is used, it will replace the existing cached entry. A change in this behavior after Windows Vista, allows for the condition when the certificate does not have a subject name, the cache is created with an index that is based on the subject key identifier and certificate issuer. If another certificate has the same the subject key identifier and certificate issuer, the cache entry is replaced. When certificates have neither a subject name nor subject key identifier, a cached entry is not created."