Does Enum.chunk_by have a bug?

Hey, @al2o3cr , thanks for taking a look.
My question is if the result is expected, if so, why?
As I see the document, it says it should create chunk when callback function returns different value.
the callback function & rem(&1,4)==0 will return like this:
[false, false, false, true, false, false, false, true, false, false]
because rem(1,4)==1, rem(2,4)==2, rem(3,4)==3, rem(4,4)==0,…
so, rem(&1,4) will be [1,2,3,0,1,2,3,0,1,2]

But, why ~c"\b" and ~c"\t\n" comes to where [8], [9,10] should be?