How late in the evening was this?
It seems to me that the CM was trying really hard to maximize counts and wanted to go for the guaranteed load instead of chancing it that the groups of guests right in front of him would equate out to six (even though if he took a moment to do a visual count of the guests, regardless of group size, her step-daughters would have been on that elevator). This could be one of two things:
1. Incompetence, which is very likely given that there have been so many threads on MiceChat in the past couple of years discussing less than average CM behavior.
2. There's a resort-wide competition that takes place internally between attractions where the attractions crews duke it out to see who can pull the highest counts per hour/day/week. I'm not sure though if this still takes place or if TDA sponsors it anymore. The last time I heard about this taking place was in 2001. During this time the grouper CMs are working on maximum efficiency mode and have been known to be a little rude at times.