I would say that this is not OK. The displays and this information is taken from the Directory database table ExchangeMailboxEntry, which is important in alot of processes.
I would say that perhaps after a sync that this would be corrected, if not then I would say there is another issue. EV queries AD etc with LDAP to discover information to populate the Exchange Mailbox Entry table. EV does not make the decision itself on what Exchange Server this user resides on.
On EV 2007 Provisioning not a sync find the user for the first time and populates the ExchangeMailbox Entry table.
There are alot of tests that could be perfomed etc that are a bit to complex to go through on the forum and in this. I would suggest that you log a call with Symantec Support and have them invesitgate it further. I have had a similar case in the past where LDAP queries for one user returned empty values and therefore would not provision. I have also seen this occur when using EVPM to enable a user. Once a sync takes place all is well again.