os-release not changed after upgrade

From: Alif Radhitya <alif_at_radhitya.org>
Date: Sat, 17 Jun 2023 02:20:42 UTC
hi, I'm radhitya, another FreeBSD user from Indonesia.

i have question for you, why my OS-release not changed after upgrade?

$ cat /etc/OS-release

NAME=FreeBSD
VERSION="13.1-RELEASE"
VERSION_ID="13.1"

i did upgrade via FreeBSD-update

my output `FreeBSD-version -u -k -r` is

13.2-RELEASE
13.2-RELEASE
13.2-RELEASE

thank you =)