As far as I know, there is no any way you can hide these things.
These Drill-down options are automatic in appearing and disappearing.
i.e. When you use Columns that have hierarchy or if you use multiple column there by bringing in hierarchy structure in the axis of the chart, then the Drill-down option will get to be displayed automatically. On the other hand when you use only one column in the axis, the Drill-down options will not be visible.
Moreover, having a hierarchy when you don't want the visual to be drilled down to give more information is a hypothetical situation. So definitely it is not a bug.
Best way to hide the Drill down options is to remove the other additional columns from the axis of the visual