Datetime inconsitencies UI/API - help needed

I spent quite a bit of work in writing scripts that return datetime for the first response on a deal and the time of the first offer sent on a deal.

While testing I found some major inconsistencies with how the api and the ui handles datetime data.

For example: I can import a datetime timestamp in both formats, e.g. 2019-01-22 08:55:59 or 2025-03-13T16:00:41.000Z and the importer UI shows the datetime as expected

However, when viewing the same info on the deal, i get only the date. When exporting the deal, I also only get the date

When viewing deal data in a list view, I also only get the date, but for the created at (a default field) I get the datetime.

That means, datetime is obviously supported.
How come custom fields dont support datetime when the UI and the API can clearly handle datetime already?
It seems like such a silly thing to not allow datetime information in custom fields or am I missing something?