BUG: %Y%m%d format with errors='ignore' doesn't return input

[MarcoGorelli]

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Reproducible Example

In [1]: to_datetime('15000101', format='%Y%m%d', errors='ignore')
Out[1]: datetime.datetime(1500, 1, 1, 0, 0)

In [2]: to_datetime('1500-01-01', format='%Y-%m-%d', errors='ignore')
Out[2]: '1500-01-01'

Issue Description

It converted to datetime.datetime instead of returning the input

Expected Behavior

'15000101'

Returning the input is what we do for literally every single other format

Installed Versions

INSTALLED VERSIONS

commit : 8dab54d
python : 3.8.15.final.0
python-bits : 64
OS : Linux
OS-release : 5.10.102.1-microsoft-standard-WSL2
Version : #1 SMP Wed Mar 2 00:30:59 UTC 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_GB.UTF-8
LOCALE : en_GB.UTF-8

pandas : 1.5.2
numpy : 1.23.5
pytz : 2022.6
dateutil : 2.8.2
setuptools : 65.5.1
pip : 22.3.1
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.6.0
pandas_datareader: None
bs4 : 4.11.1
bottleneck : None
brotli : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
zstandard : None
tzdata : None
None

[MarcoGorelli]

dupe #14487