Maybe you don't have any plants, but inadvertently turned on the plant sizing option shown in the screenshot. Normally OpenStudio leaves this option off in the model, and then turns it on when creating the idf file if there are plants.

https://github.com/NREL/OpenStudio/blob/develop/openstudiocore/src/energyplus/ForwardTranslator/ForwardTranslateSimulationControl.cpp#L81