Description of problem:
If a user wants to manually manage the sub[ug]id ranges before he creates the users those changes don't get reflected in /etc/subuid and /etc/subgid

Version-Release number of selected component (if applicable):
# rpm -qa|grep shado
shadow-utils-4.6-12.el8.x86_64

How reproducible:
always

Steps to Reproduce:
1. echo container:493216:65536 >> /etc/subuid 
   echo container:493216:65536 >> /etc/subgid 
2. useradd container 
3. cat /etc/subuid 
  container:493216:65536 
  container:558752:65536

Actual results:
I see two independent entries for the same user with different ranges. The first one is the expected one which I put manually. The second one comes from useradd and is auto generated.
According to the man page of useradd this should NOT happen:
       SUB_GID_MIN (number), SUB_GID_MAX (number), SUB_GID_COUNT (number)
           If /etc/subuid exists, the commands useradd and newusers (unless the user already have subordinate group IDs) allocate SUB_GID_COUNT unused group IDs from the range SUB_GID_MIN to SUB_GID_MAX for each new
           user.

           The default values for SUB_GID_MIN, SUB_GID_MAX, SUB_GID_COUNT are respectively 100000, 600100000 and 65536.

       SUB_UID_MIN (number), SUB_UID_MAX (number), SUB_UID_COUNT (number)
           If /etc/subuid exists, the commands useradd and newusers (unless the user already have subordinate user IDs) allocate SUB_UID_COUNT unused user IDs from the range SUB_UID_MIN to SUB_UID_MAX for each new
           user.
I want to highlight "unless the user already have subordinate group/user IDs"

Expected results:
useradd honors the predefined values in /etc/subuid, /etc/subgid and doesn't add different values for the new created user.

Additional info: