Splitter proportion, doesn't respect values approaching 0 or 1

I would expect that setting splitter proportion to 0 or 1  will behave as stated, instead there is always some text + tabs (I wouldn't mind tabs being retained, but I absolutely mind the text), this makes it annoying when I want to have something like focus/expand action where I would completely extend editor in question.

Values like .33, .25, .5 work as expected bat at low values tis breaks.

Is there some hidden option that would allow me to splitter truly respect its API and expand to 100%?