I'm not sure if this is by design, but blank entries sort high in the activity lists. That means if you have a graph with lots of activities, many of which aren't executed, if you sort by the maxelapsedtime stat, the largest values occur in the middle of the list. low values at the start, and blank values at the end.

I suspect it would be better to sort them below 0. An option to remove nulls would be even better....