If the tenant doesn't return the condition report with their comments etc, then the owner's / property manager's version stands as the only valid version of the report.
We tell all our tenants that the entry condition report is the most important document in their tenancy, and give them a whole week to return it (instead of 3 days)..... I still get no more than 1 in 5 back. If they don't return it in time, the agents copy stands. I haven't had a problem in years anyway since we generally use the photos to clarify any discrepancy, the paper reports are becoming a bit outdated.