I think the onboard bidding was a temporary work around to continue to generate revenue on excess capacity whilst the pre boarding process was in abeyance due to the IT meltdown. It was a lot of work for guest relations during their busy early days of the cruise and didn’t give any recognition for loyalty which was always a stated focus of the upgrade process. It was much more a first come first served action once the ship was sure of its inventory (a slight (!) issue during the IT meltdown).
Looks like they’ve now reverted to a version previously used with the significant added benefit of the guest having the final say on accepting the upgrade or not.