bug in basename ?

[dtoppin]

In using basename I ran across the following condition
that seems to be incorrect:

    basename a.b/c .b

Produces:
    c


info basename says that the suffix is removed only
if it is identical to the END of the name.
Am I reading this incorrectly?

The basename I'm using is:
    basename --version
    basename (GNU sh-utils) 2.0

thanks
Doug