The Spatial Modeler does not update function variables when input files are changed. For example, if a spatial model file (*.gmdx) is used periodically with new input raster images then the new image name is not updated in the function syntax. Complicated models can become difficult to interpret. The spatial models will run, but it is incredibly challenging to debug a model that has nonsensical variable names when the model is used repeatedly with new input data.
This is not a new issue with the Spatial Modeler. The old Classic Model Maker and the Spatial Modeler in IMAGINE 2013 and 2014, had the same issue. They both use the image name as the name for the raster inputs.
In the new Spatial Modeler you can rename your raster inputs and outputs. Just right-click on a raster input operator and select "Rename". You can then name it "Input" so in the next operator the 'input' will show up as the raster input object