Any idea why I am getting a 2 bags allowed on the outbound but only one back on the inbound from KLM MMB?
Assume MMB applies the following logic - not necessarily correct as has been pointed out:
Outbound, your KLM Platinum allowance of 2 bags is displayed for both the 1st KLM segment and the subsequent EI segment.
Inbound, your KLM Platinum presumably doesn't give you anything extra on EI so it will display a single checked bag allowed, on the assumption that you won't bother to check a second bag at AMS while changing planes...