Default user 'postgres' not mentioned in the documentation?

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/postgres-user.html
Description:

Hi

I'm a newbie and may be asking stupid questions... but 
shouldn't it be mentioned in the official documentation on this page
https://www.postgresql.org/docs/12/postgres-user.html
that postgresql upon installation automatically creates a system-user that's
called 'postgres' ?

I thought it was odd that I had to find that information on other websites

(e.g. here:
https://medium.com/coding-blocks/creating-user-database-and-adding-access-on-postgresql-8bfcd2f4a91e)

Now I'm still confused, if the docs want to tell me I should create yet
another user for safety reasons or if that's not necessary...

Thanks for clarification, any comment is valuable to me
Best regards