 BUG: iloc setting columns not taking effect
- [x] closes #33198
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

are you running the full test suite locally before pushing? > are you running the full test suite locally before pushing?

Not fully. usually only the parts I suspect that are related to the changes I make, in this case I tried on ```pytest -q --cache-clear pandas/tests/frame/methods/``` before pushing. Unless you need to save the wattage, its usually good to run the full thing.  e.g. i have in .bash_aliases `alias ptest="python3 -m pytest pandas/tests --skip-slow --skip-db"`

In this case we might expect tests.indexing, tests.frame.indexing, tests.series.indexing, and possibly tests.indexes to be potential trouble spots > Unless you need to save the wattage, its usually good to run the full thing. e.g. i have in .bash_aliases `alias ptest="python3 -m pytest pandas/tests --skip-slow --skip-db"`

That's a good tip.
 Looking at the test logs, there's still some more troubleshooting to be done.  What's the next step? > Looking at the test logs, there's still some more troubleshooting to be done. What's the next step?

@jbrockmendel Looks like we need to check for the length of the index of each one, to decide if we are taking the split path.

what I tried was:

```python
                val = list(value.values()) if isinstance(value, dict) else value
                # https://github.com/pandas-dev/pandas/issues/33198
                if isinstance(indexer, tuple) and com.is_null_slice(indexer[0]):
                    take_spit_path = length_of_indexer(
                        self.obj.index
                    ) == length_of_indexer(indexer[0])
```

---

But it does not work.
 Let's continue troubleshooting in #33198.  Closing to clear the queue, can re-open when its ready to go.