BUG: Series[listlike_of_ints] incorrect on MultiIndex
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

This is one of the cases that @jorisvandenbossche identified in #33355.
whatsnew added + green rebased+green