I am using ArcGIS Desktop 10.5.1 Standard / Windows 10 Pro.
I am selecting features with a common attribute and then using the Create Layer from Selected Features method to create a new layer to work on. As soon as I sort my new selection layer, its feature count jumps back to the original feature count of the source layer. In effect, I now have a new layer that is an exact duplicate of the source layer.
Are there certain conditions with the source data that might cause this behavior?