git describe not showing "nearest" tag

$ git rev-list --count v3.2..master 9651 $ git rev-list --count v3.3..master 6378 $ git describe --tags master v3.2-9651-ga018267

I would have expected to see v3.3-6378-ga018267, given the documentation:

  If multiple tags were found during the walk then the tag which has the
  fewest commits different from the input committish will be selected
  and output. Here fewest commits different is defined as the number of
  commits which would be shown by git log tag..input will be the
  smallest number of commits possible.

What's going on here?

The repository: https://bitbucket.org/petsc/petsc

This repository currently uses only lightweight tags. As an experiment, I replaced both v3.2 and v3.3 with annotated tags, but it did not affect the 'git describe' output.