Yes, I know. That's why I'm here. (because the info entered to bucket alias is more valuable than just to creates a CNAME record.)
If you ask for CDN name to see the actual problem for yourself, I suggest you try Cloudflare since it's free.
However, if you already know how DreamObjects' CNAME mapping works (You supposed to because you are the one who confirmed my theory here
https://discussion.dreamhost.com/thread-136188-page-2.html ) it seem like you don't know how origin pull CDN works!
So, let me explain
Origin pull CDN typically has 2 main components
1 DNS server
2 caching reverse proxy
let say I have a website example.com and use cdn.example.net as CDN
I have to use ns1.cdn.example.net and ns2.cdn.example.net as nameservers for my example.com website so I have to manage DNS record in control panel of cdn.example.net.
I can put CNAME record that point from "do.example.com" to "bucketname.objects.dreamhost.com" there and it will work as you expect
until I active CDN functionality on "do.example.com".
because when the CNAME record actually pointed to "bucketname.objects.dreamhost.com" the visitors will connect directly to Dreamhost's server there is no opportunity for caching proxy to kick in.
So, origin pull CDN modify this CNAME record to point the visitors to caching proxy server instead of origin server.
Now we have CNAME record that pointed to "cache.cdn.example.net" instead of "bucketname.objects.dreamhost.com".
"cache.cdn.example.net" is part of CDN system so it will know that it should send requests to "bucketname.objects.dreamhost.com" regardless of "bucketname.objects.dreamhost.com" is in actual DNS record or not.
but when DreamObjects query "ns1.cdn.example.net" and got "cache.cdn.example.net" it cant determine the bucket name. (since the bucket name is not there.)
but now you have new feature/UI that intend to just control DNS records. The values entered there can also use as explicit bucket pointer (no need to query DNS for a bucket name anymore).
It solve CDN conflict and can also improve overall system performance.
It sound good, isn't it?
P.S. If you have hard time explain this issue to other dreamhoster please allow me to join your conversation. my English is not perfect (because I'm Thai) but my communication skill is relatively high.