why would it not return this result?

01/04/2025 is april 1st 2024 (given format 103 being dd/mm/yyyy) and 12pm is midnight, aka 00:00 (which is the result you get from converting a date to datetime)

if you're asking specifically about the format itself (why am/pm instead of 00:00) a quick glance at sql server documentation points to SET LANGUAGE and SET DATEFORMAT having an effect on this