Downside with this is that they have to pay someone to review, they will still miss miss problems unless they simply skip anything who is not item or simple config mods.
After they stop make DLC they will also reassign the guy doing testing.
Now the manual review process also raise an issue, how do you test that an mod work well on One in the fist place.
You will need some sort of backdoor for testing mods. If the official channel is to narrow the backdoor will be the default way to do stuff.