Pandas read_excel function ignoring dtype

I'm trying to read an excel file with pd.read_excel(). The excel file has 2 columns Date and Time and I want to read both columns as str not the excel dtype.

Example of the excel file

I've tried to specify the dtype or the converters arguments to no avail.

df = pd.read_excel('xls_test.xlsx',
                   dtype={'Date':str,'Time':str})
df.dtypes
Date    object
Time    object
dtype: object

df.head()
Date    Time
0   2020-03-08 00:00:00 10:00:00
1   2020-03-09 00:00:00 11:00:00
2   2020-03-10 00:00:00 12:00:00
3   2020-03-11 00:00:00 13:00:00
4   2020-03-12 00:00:00 14:00:00

As you can see the Date column is not treated as str...

Same thing when using converters

df = pd.read_excel('xls_test.xlsx',
                   converters={'Date':str,'Time':str})
df.dtypes
Date    object
Time    object
dtype: object

df.head()
Date    Time
0   2020-03-08 00:00:00 10:00:00
1   2020-03-09 00:00:00 11:00:00
2   2020-03-10 00:00:00 12:00:00
3   2020-03-11 00:00:00 13:00:00
4   2020-03-12 00:00:00 14:00:00

I have also tried to use other engine but the result is always the same.

The dtype argument seems to work as expected when reading a csv though

What am I doing wrong here ??

Edit: I forgot to mention, I'm using the last version of pandas 1.2.2 but had the same problem before updating from 1.1.2.

from Pandas read_excel function ignoring dtype