Answer
By default, ArcGIS does not apply a standard deviation stretch renderer to MrSIDs. This is because MrSIDs are usually stretched when they are encoded from the original raster.
The default setting for all other raster types, including all geodatabase raster catalogs, is to apply a Standard Deviation stretch renderer to the rasters. It is recommended to change the renderer for the raster catalog, saving the layer to a .lyr file, and use this .lyr file to add the raster catalog to ArcMap.