$ pkg-config --help
[...]
  --atleast-version=VERSION               return 0 if the module is at least version VERSION
  --exact-version=VERSION                 return 0 if the module is at exactly version VERSION
  --max-version=VERSION                   return 0 if the module is at no newer than version VERSION

While the source code states that it causes the version requirement in read packages to be replaced with the given one instead:

        if (required_exact_version)
          {
            g_free (ver->version);
            ver->comparison = EQUAL;
            ver->version = g_strdup (required_exact_version);
          }

Although the return value usually will be a side-effect of this change, the description suggests that it implies behavior like '--exists'.