Min-step for horizontal chart granularity scaling

Our charts don’t seem to scale the interval as the time window grows. We’ve left min-step empty, and according to the tool-tip:

“Leave blank for auto handling based on time range and panel width. Note that the actual dates used in the query will be adjusted to a multiple of the interval step.”

However, the charts always seem to use all the data, I would have expected them to aggregate data points together to provide a less granular view as the time range expands.

Our query is:

sum( sum_over_time( total_requests[$__interval] ) ) by (EntityName)

The config is blank for Options-Min time interval & also blank for the Min step value on the query definition.

What are we doing wrong?