Evolution charts and row evolution uses the method
Metrics::getUnit to determine the unit that should be shown with any metric.
For new plugins having custom metrics there is currently no possibility to manipulate that behavior. This causes all metrics, that don't match the format handled by the core method, to be shown as numbers only, even if they should be percent or time values.
The new event will make that possible.
LGTM, not sure if there's more to the
getUnit() method vs event discussion