It's inconsistent now in any case:

__setattr__(..., bytes) -> sets unicode ?
__setattr__(..., list(bytes)) -> sets list(bytes)

Also, as far as I can see, passing a string is broken now because list('abc') = ['a', 'b', 'c']...

Before 954825e17c5f979c87d51d6bc18347133fb119b2 __setitem__ expected either bytes or unicode. But then it was changed that each parameter internally contains a list which was generated by splitting the value along the pipes when the value was bytes or unicode. And with that it allowed devs to add lists themselves containing any type and it wouldn't touch these. It converts only bytes/unicode into the list.

Also __setitem__ doesn't “convert“ any values anymore with my change but instead now only _encoded_items and that is not modifying the dictionary Request is using to hold the parameters. So yes the docstring is not up to date but there is a reason behind all of that.