No behavior change intended.
Many file drag & drop handlers used the icon assigned for dragging to
determine what type of data is dragged. This is fragile, for example
changing an icon would break drag & drop (!). This happened a few times,
e.g. see 3788003cda. It's also causing problems with #104830, which
changes how file browser drag data is handled.
Instead use the file extension to determine the file type.