Upgrades require upgrade inventory, not just an empty seat until T-30. Chances are that there are higher tier elites ahead of you on the upgrade list, which you can't see until check in.

Your guess about 3 of 5 for 4 is right and if the data is from close to departure time (not T-24, for example, when people are first able to do OLCI and see their preliminary positions on the list) #3 would have a good chance of being upgraded at the gate right before boarding begins unless it's the sort of flight where passengers are likely to purchase upgrades or purchase last minute premium cabin tickets.