BUG: setting dt64 values into Series[int] incorrectly casting dt64->int
- [ ] closes #xxxx
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

> sure but i thin it is much more clear to use an elif and then simply repeat that line in the else

ok, will update.

BTW #38709, #39044, #39163 also touch this code, will need to get those merged/rejected in order to move forward on the refactor in #39302.

(and a very gentle ping on #38992 since I want to write more tests) rebased + green lgtm. can you merge master and ping on green