Army General Coop DLC requirements

[Terminus of Existence]

Hi yall, from my understanding, to play Army General in coop with friends, only one friend needs to own the campaign itself to host it, other players do not. However yesterday while attempting to play one of the campaigns yesterday, we were unable to do so and had to do one that we all owned.

Are we incorrect that only the host needs to own a dlc to play a coop campaign?

[SKL-1]

Both need the DLC