Inconsistent element types when using to_physical on List(Datetime) vs Array(Datetime, ...)

[egorchakov]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

from datetime import datetime

import polars as pl

series = pl.Series(values=[[datetime.now()]])  # noqa: DTZ005

for dtype in (pl.List(pl.Datetime), pl.Array(pl.Datetime, 1)):
    print(f"{dtype}: {series.cast(dtype).to_physical().to_list()}")  # noqa: T201

Log output

List(Datetime): [[1729688789716971]]
Array(Datetime, shape=(1,)): [[datetime.datetime(2024, 10, 23, 13, 6, 29, 716971)]]

Issue description

Calling to_physical on a Series(dtype=List(Datetime)) casts the inner elements to an integer type, which is not the case for a Series(dtype=Array(Datetime, ...)).

Technically this behaviour does match the doc, but the inconsistency does seem surprising.

Expected behavior

to_physical on container types produces the same inner element type regardless of container type.

Installed versions

--------Version info---------
Polars:              1.10.0
Index type:          UInt32
Platform:            macOS-14.4-arm64-arm-64bit
Python:              3.12.4 (main, Jul 25 2024, 22:11:22) [Clang 18.1.8 ]
LTS CPU:             False

----Optional dependencies----
adbc_driver_manager  <not installed>
altair               <not installed>
cloudpickle          3.1.0
connectorx           <not installed>
deltalake            <not installed>
fastexcel            <not installed>
fsspec               2024.10.0
gevent               <not installed>
great_tables         <not installed>
matplotlib           3.9.2
nest_asyncio         1.6.0
numpy                1.26.4
openpyxl             <not installed>
pandas               <not installed>
pyarrow              17.0.0
pydantic             2.9.2
pyiceberg            <not installed>
sqlalchemy           <not installed>
torch                2.5.0
xlsx2csv             <not installed>
xlsxwriter           <not installed>