The problem is that over time it might wear down with the caribiner always rubbing against it. This was my concern as well because I have experienced this first hand on a 2nd hand bag. In particular an older chimp. It didnt have d rings on the bottom hookups and you could clearly see the wear from the caribiner,ut was hlfway "cut" through. What the d ring does is eliminate the fabric from being "cut" over time. Granted it takes a long time to have this problem im sure,but it still happens.
There is a chance of the d ring breaking also unless its metal but we'll see how the loops hold up. obviously these bags havnt been around long enough to see them worn in like other bags
Its not a big deal but after experiencing that priblem first hand,it popped into my head too