Fixed #12651: providing links to the .cum* in .expanding
- [x] closes #12651
- [ ] tests added / passed
- [ ] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry
  #12651
  
  commit for the .cum\* in .expanding

Should close #12651 (not #12561).

I think it is better to link each other via docstring as described in #12561, or use section links ( `..sealso::` ). It's unclear what the updated part tries to explain.
 sectional links provided.
 pls reopen if you like to update according to comments
