I have the book by Trizzoni, I think the guy is barking.
The Germans didn't care about Trieste, they needed Ariete to move to Bir Bu Cremeisa. Ariete received the order on 4 December clearly specifying to get going that evening and to complete the move during the night, and then spent all of 5 December stationary. Not sure how Gambara is to blame for this.
All the best
Andreas