BUG: Setting a DataFrame as rhs with loc on a single column does not align in the single block case

[phofl]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

result = pd.DataFrame({"var": [1, 2]}, index=[1, 2])
rhs = pd.DataFrame({"var": [10, 11]}, index=[2, 3])
result.loc[:, "var"] = rhs

returns

   var
1   10
2   11

This does not align, because it runs through the single_block_path, while non-matching dtypes do align

result = pd.DataFrame({"var": [1, 2]}, index=[1, 2])
rhs = pd.DataFrame({"var": ["a", "b"]}, index=[2, 3])
result.loc[:, "var"] = rhs

   var
1  NaN
2    a

Issue Description

Should be consistent

Expected Behavior

Both should align. First one should return

   var
1   NaN
2   10.0

Installed Versions

commit : 55d9dcf
python : 3.8.13.final.0
python-bits : 64
OS : Linux
OS-release : 5.15.0-40-generic
Version : #43 SMP Wed Jun 15 12:54:21 UTC 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.5.0.dev0+1066.g55d9dcf47d
numpy : 1.22.4
pytz : 2022.1
dateutil : 2.8.2
setuptools : 62.3.2
pip : 22.1.2
Cython : 0.29.30
pytest : 7.1.2
hypothesis : 6.47.0
sphinx : 4.5.0
blosc : None
feather : None
xlsxwriter : 3.0.3
lxml.etree : 4.9.0
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.4.0
pandas_datareader: None
bs4 : 4.11.1
bottleneck : 1.3.4
brotli :
fastparquet : 0.8.1
fsspec : 2021.11.0
gcsfs : 2021.11.0
matplotlib : 3.5.2
numba : 0.53.1
numexpr : 2.8.0
odfpy : None
openpyxl : 3.0.9
pandas_gbq : None
pyarrow : 8.0.0
pyreadstat : 1.1.7
pyxlsb : None
s3fs : 2021.11.0
scipy : 1.8.1
snappy :
sqlalchemy : 1.4.37
tables : 3.7.0
tabulate : 0.8.9
xarray : 0.18.2
xlrd : 2.0.1
xlwt : 1.3.0
zstandard : None
None

[simonjayhawkins]

First one should return

   var
1   NaN
2   10.0

This was the case in pandas-1.3.5

first bad commit: [03dd698] BUG: DataFrame.setitem sometimes operating inplace (#43406)