While looking to see if anyone had requested this, I found a support request that someone had created talking about it, but no actual submission.
In Circle v2, developers can create workflows of different steps. Steps have different purposes and can take vastly different amounts of time. Each step of a workflow generates a separate build as the workflow is run.
However, inside insights, it's impossible to distinguish between the different types of step in a workflow, and therefore averages like "Median" become useless as a measure of build health.
The insights product should recognise workflow builds, and provide separate metrics (and possibly separate graphs) for each step.