The Pie Chart Report and Single Level Group By Report allow users to organize issues by a Statistic Type parameter. Currently, this includes most system fields and almost all custom fields (any instance of CustomFieldStattable - which includes most built-in custom field types). The Statistic Type parameter ignores both the field configuration and custom field context.

This may confuse users on a large Jira instance with many custom fields. Even if a Jira administrator has taken the time to optimize custom field contexts (Optimizing custom fields), the dropdown will still include these custom fields. This causes the results to display irrelevant for the statistic.

Custom field context

Report parameters