Of course that's what the officer testified. If he'd said that he had any suspicions, it would have only strengthened the case against him. The car was not taken into extended custody and, it would seem, was never out of sight of the driver. The car was not being impounded nor was there a threat to the officer's safety, which would be the only reasons that an "inventory" would be necessary.
It was in police custody, hence the policy of an inventory check. I suppose you'd rather the officer take it on the chin when he doesn't do the inventory check and the allegation comes in after the fact.