Drag&Drop is an interaction between 2 programs.
After a D&D action the receiving program gives a feedback of what the action should be interpreted.
The possible feedback ist the following:
0 DROPEFFECT_NONE Drop target cannot accept data.
1 DROPEFFECT_COPY dropping invokes copying.
2 DROPEFFECT_MOVE dropping invokes a move
4 DROPEFFECT_LINK dropping creates a link
The source application then acts accordingly. So apparently some of your applications report "move" and others "copy". Mp3tag does not influence these applications.