OO.ui.mixin.DraggableElement has two ways to set its draggable state - via the constructor config, or via the toggleDraggable method.

There is a list of problems in this redundant implementation.

Via the constructor:

• the class oo-ui-draggableElement-undraggable, indicating that the object is not supporting dragging at the moment, is not added (compare toggleDraggable method)
• the draggable attr does not get set based on the object property but is always true (might not have negative effect, but is weird)

Via the toggleDraggable method:

• large parts of the method are only run if a change to the object property is performed. That means that calling toggleDraggable(false); stays without effect after constructing the object with config { draggable: false } and leaves the object in an undesired state (while specifying the opposite twice)

Might be what T129184 tried to describe.