I'm assuming there were multiple accounts on this server. Depending on how the discovery request was worded, if the VIP's email address was removed or modified from the from / to headers of emails, one could reduce the set of emails that have to be handed over 'where the VIP was included in the conversation'. Or perhaps remove embarrassing email addresses that were cc'd/bcc'd on sent mail.
The danger is that another party to the chain still has a copy of the email that shows it in a different state then would be in the archive which would expose the subterfuge.
Perhaps it was that concern that resulted in deleting emails rather than modifying them, as perhaps destruction of records is far less of an issue then falsification of records.