COO sells three products in a 4 department store

[pulsar1013]

Hello, I am sorry if this topic is discussed before, I did a search and found nothing

When I appoint a COO to manage my retail stores, he tends to sell three products regardless if I have set 4 departments. This means, he uses two departments to sell identical items. I would like the COO to sell four products, each for my separate department, this normalizes my logistics network greatly

Is there a setting I can tweak or is this a game mechanic I can do nothing about?