LineCap=none ,still rendered in _width (bug?)

[McUsher]

Ok,
i don't have questions often, but as this might be a bug,
i am out of ideas:

I have movieClip with a square in it, which has horizontal lines.
The caps of the lines i set to "none" as i will need to set/get
the width of that square without those bloody round caps
(was giving me headaches in the flash versions b4 8ball).

But even, if the caps are set to "none" the round ending
will render into the width of the MC the lines are in.
Is this a Bug, or is this working as inteded ?

Just incase i expressed myself unclearly i provide a fla.

Any other workaround, but setting mc._width = widthWanted+lineThickness?