Setting the minimum shading rate to 0.02 shouldn't make a difference unless you have changed the shading rate on all items in the parameters dials as well. The render settings shading rate only takes prededence if an objects' shading rate is lower, so for example if an object in your scene had a shading rate of 0.01, then the render setting shading rate of 0.02 would take priority. If your scene object has a shading rate of 0.2, that is what gets used, not the 0.02 in the render settings.

According to the manual, anyway.