Yes, the new CO can require other evidence of whatever kind if he feels it is necessary. Many other people have thought their case was completely finalized, and knew it had been sent to second-person checking, and then found that the 2pc official found one or two more areas where more checking and evidence was required.
I can understand your feeling rather disappointed that this should have happened, but do remember, the application for a visa is a request, and not like buying something where you have solid certainty that when you hand over x, you will receive y. INZ says jump, and the applicant says, 'How high?'