Flow is more important than maximum speed.
Agility is not a tool to maximize efficiency. Squeeze more out of an org, team or process is the old way to do it. Agility is to maximize the work not to do. By the way the resources where focused on the most valuable ones. With the resources allocated the maximum outcome is generated.
A KPI suitable for that paradigm is not velocity. If we would use that, the team will drive the velocity KPI, but the generated outcome is still the same – because the outcome can no longer rise.
An idea is to measure consistency of flow and predictability. This is valid for Scrum as well as for Kanban. The target is to minimize the variance.