As far as I know, NTLM got a set list of host-names it will authenticate with. When just creating an alias like that, without updating it on the "server side" the auth will fail.
I found two relating articles regarding a few windows flavors :-)
Link 2 - Regarding access on 2003 server
As it seems both need the server-side to be updated to work, I believe you're correct in assuming this is due to the nature of NTLM.