1. Select a file or folder 2. Start a drag of another file or folder. Both files/folders are selected. This could make the user think both were being dragged. Also, if someone escapes out of a drag, they probably want only what they had selected for the DND to be selected
Additional information: You can even select ad infinitum if you escape each DND.
This is the two click drag method. If you want to drag a single file, click-release-click and drag. This is to make multiple drag selection easier. If you click and hold, previous selected items are reselected. If you don't want the two click drag method, you can choose the one click drag method from the option menu. The one click drag method is the default gtk behaviour, but many people simply do not understand how to select multiple files using the default gtk one click method. The option for one click-method is not available in the 4.0.x series (>=4.0.1)