Why can't I use git-bisect to find the first *good* commit?

Something was broken a 100 revisions ago, has now been fixed, but I want to find when it was fixed.

I'd expect this to work:

    $ git bisect start
    $ git bisect good
    $ git bisect bad HEAD~100
    Some good revs are not ancestor of the bad rev.
    git bisect cannot work properly in this case.
    Maybe you mistake good and bad revs?

But instead I have to do:

    $ git bisect start
    $ git bisect bad
    $ git bisect good HEAD~100

And then proceed to mark good revisions as bad, and bad revisions as good.

That works, but it's very confusing.

Why can't bisect just do the right thing here and accept that your more recent revesion is the good one, and the old one is the bad one?