I just ran into the same problem: Calling setBackgroundDrawingCallback with a nil value will lead to problems - #2 by matt
So I would like to know what the status of this issue is.
If the implementation is not changed, then at least the documentation (and maybe examples using this) should reflect that the result of the call can and should be used (to remove it and avoid having multiple backgrounds).
I feel like that is not obvious without looking at the implementation (which few people probably do).