In beta this option opened up a dialog box that allowed you to select a face to be separated from the part. Now the command doesn't allow the user to select what face to separate, it just splits every face of the part and make them their own part.
The old way was better. Now I have to select all the faces that I didn't want separated and merge them. Or am I missing something?
Maybe it's a matter of Standard vs Professional?
Try enabling the blue Part Selection tool from the main Toolbar, then right click in the Viewport on the part you want to split and select Extract Part.
Although your workflow should also bring up the Part Splitter wizard, try my recommendation above and let us know if it works.