Hi César,
You have done an excellent analysis and logically speaking KMEIN should be delta-relevant. Moreover because it is part of the main structure MCKOMV.
I think it might be time to create an SAP Support message. Supply your detailed analysis in the message and also mention the release/SP details and which SAP Notes you reviewed.
Please keep us updated because I would like to know the cause of this issue.
Thanks,
Sander