That makes no sense - empty seats means more people wait. Also, not quite sure what you are trying to say happened in your first sentence? Every time we have loaded as an odd numbered group, we have gotten on quickly, as they load one car odd, one car even. That way, they don't have to stop and try to find singles/pairs to fill empty eats, or send out cars with 2-3 empty seats.
20 riders will fit in each train. The ride takes less than 3 minutes. If they leave even 1 seat empty, that's 20 riders per hour not going on. On a typical 13 hour day, that's 260 people not getting on. I hope they go back to odd/even to get those seats filled.