This has no effect on the editorial review decision but I would like to comment.
If I put up a site that simply sells Amazon books then I am doing so with the endorsement of Amazon. But I don't have any unique content, I am simply another doorway into the Amazon catalogue. We deem that an affiliate and it is strictly forbidden to list affiliate sites.
I could call myself something else, a reseller, or an agent, or a service provider maybe. But the basic business model remains the same, I am merely a doorway to someone else's products.
The fact is, in this case, that DIMIA has a direct service and that service is listed. Specifically to allow our users to go straight to the source. As Amazon is listed so there is no need for our users to go via one of their affiliates/resellers/agents/service providers. Our alternative is to go to DIMIA and ask them to provide the URLs for all their agents, and list the lot in the interests of fairness. But as you can guess, that is the last thing we would do! I do find it somewhat odd that if DIMIA is actually encouraging the use of its agents that it does not list them on its own site. Yours is not the only ETA issuer site to be rejected for the exact same reasons BTW.
it is not possible for all persons to know or find the DIMIA on the Internet to arrange their ETA.
But on DMOZ they can, very easily. That is why it is listed.