id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1384465119,I_kwDOAMm_X85ShULf,7076,Can't unstack concatenated DataArrays,22566757,open,0,,,9,2022-09-24T00:50:09Z,2023-02-21T17:11:35Z,,CONTRIBUTOR,,,,"### What happened?

I had a collection of `DataArray`s with a stacked dimension (dimension whose corresponding index is a `MultiIndex`). I concatenated them into a single `DataArray`, then tried to unstack the stacked dimension, which failed.  Performing the operations in the other order works (unstacking each `DataArray`, then concatenating the unstacked arrays).

### What did you expect to happen?

I expected that concatenating the arrays then unstacking them would produce the same array as unstacking them then concatenating them, but with the possibility of saving the intermediate concatenated-but-still-stacked `DataArray` for later use as a template.

### Minimal Complete Verifiable Example

```Python
import pandas as pd
import xarray
index = pd.MultiIndex.from_product([range(3), range(5)])
arr = xarray.DataArray.from_series(pd.Series(range(15), index=index)).stack(index0=[""level_0"", ""level_1""])
arr.unstack(""index0"")

arr2 = xarray.concat([arr, arr], dim=""index2"")
arr2.unstack(""index0"")
```


### MVCE confirmation

- [X] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
- [X] Complete example — the example is self-contained, including all data and the text of any traceback.
- [X] Verifiable example — the example copy & pastes into an IPython prompt or [Binder notebook](https://mybinder.org/v2/gh/pydata/xarray/main?urlpath=lab/tree/doc/examples/blank_template.ipynb), returning the result.
- [X] New issue — a search of GitHub Issues suggests this is not a duplicate.

### Relevant log output

```Python
<xarray.DataArray (level_0: 3, level_1: 5)>
array([[ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14]])
Coordinates:
  * level_0  (level_0) int64 0 1 2
  * level_1  (level_1) int64 0 1 2 3 4

Traceback (most recent call last):
  File ""<stdin>"", line 1, in <module>
  File ""~/.conda/envs/plotting/lib/python3.10/site-packages/xarray/core/dataarray.py"", line 2402, in unstack
    ds = self._to_temp_dataset().unstack(dim, fill_value, sparse)
  File ""~/.conda/envs/plotting/lib/python3.10/site-packages/xarray/core/dataset.py"", line 4618, in unstack
    raise ValueError(
ValueError: cannot unstack dimensions that do not have exactly one multi-index: ('index0',)
```


### Anything else we need to know?

The eventual problem to which I wish to apply the solution has two stacked dimensions rather than one, but that's likely irrelevant.

### Environment

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 3.10.6 | packaged by conda-forge | (main, Aug 22 2022, 20:35:26) [GCC 10.4.0]
python-bits: 64
OS: Linux
OS-release: 3.10.0-1160.76.1.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.12.1
libnetcdf: 4.8.1

xarray: 2022.6.0
pandas: 1.4.2
numpy: 1.22.3
scipy: 1.8.0
netCDF4: 1.6.0
pydap: None
h5netcdf: None
h5py: None
Nio: None
zarr: None
cftime: 1.5.1.1
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: 3.2.1.post0
bottleneck: 1.3.5
dask: 2022.7.1
distributed: 2022.7.1
matplotlib: 3.5.1
cartopy: 0.20.3
seaborn: 0.12.0
numbagg: None
fsspec: 2022.5.0
cupy: None
pint: None
sparse: None
flox: None
numpy_groupies: None
setuptools: 61.3.1
pip: 22.0.4
conda: 4.14.0
pytest: 7.1.3
IPython: None
sphinx: None


</details>
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