Doubt in reset date style - Mailing list pgsql-bugs

Hi Team,
I have a doubt in the expected output file: src/test/regress/expected/horology.out

at https://github.com/postgres/postgres/blob/913c60b067aa1a618420fd0372c4df3cf5501863/src/test/regress/expected/horology.out#L117.

After doing the reset DateStyle.
Why output is still in 'Postgres, MDY' form rather than 'ISO, MDY'. As reset would have reset the datestyle value to default value as 'ISO, MDY'. I don't see any Alter cmd which changes the default value of DateStyle as well.
Can you please correct me why this Pg Behaviour is expected.

Thanks In Advance!